FI108649B - Process for the production of fuel by composting and a tunnel composting plant - Google Patents

Description

108649

METHOD FOR THE MANUFACTURE OF FUELS FOR COMPOST COMPOSITION AND THE TUNNEL COMPOSITION FACILITY

The invention relates to a method and a tunnel composting plant 5 for the production of fuel from organic materials, in particular sludges and possible auxiliary materials, by means of mechanical composting. The organic materials are first brought to a dry solids content, generally about 30%. The mixed and thus pre-dried masses are divided into mechanical and batch composting sats, which are first dried by composting the masses of each sats so that the cellular structure of the organic material is disrupted to allow for thermal drying and their moisture content is reduced to 65-55%. The heat produced by the compost-15 is then used to dry the pulps in a separate drying step, in which the sats are generally dried to about 50%.

The heat generated by composting is used to dry the pulps. Organic materials include fiber sludges, bio sludges, pasta sludges and / or peeling sludges from the pulp and paper industry, but also, for example, from the pulp and other organic pulps of the wood processing industry.

• · · i »t •., 25 Slurries from the pulp and paper industry can be divided into: mainly sludges.

• · · · - fiber sludges, mainly so called zero fiber (wood fiber), - bio-sludges, biological sludge sludges, *: * *: - pasta sludges, kaolin-containing pasta sludge, • 3δ - crust sludges, ···, Although the fiber sludge can be mechanically dried up to 40% sludge, preferably mixed together to form a '• f mixed slurry, since especially the biological slurry (mostly' ••• 35 bacterial masses) cannot be dried to more than 12-16%. For example, the mixed slurry is dried to 30% with a steam screw press.

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Mixed sludge is currently burned in bark boilers, with other uses being small and difficult. The problem is the low solids content of the sludge, which results in loss of boiler capacity and increased emissions and costs. Thermal drying 5 is also expensive (high drying temperature), in addition to which odor nuisances occur during the drying process. The water in the organic pulp is so bound to the cellular structure that its removal by thermal drying or compression requires an excessive amount of energy.

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Finnish patent 100191 describes a process for making fuel from organic sludge or biowaste. According to the method, the slurry is dried by composting and collecting the nitrogen discharged during composting in a scrubber. Composting provides several benefits. The quality of the pulp is homogenized and the harmful microbes in it die. On the other hand, part of the combustion value of the pulp is lost in composting. The heat generated by composting is usually wasted.

. Swedish Patent Publication No. 447827 discloses a core-composting method with an air-based base for drying the aqueous I · · · · '/ pulp, in particular the pulp mass, as a fuel.

Exhaust air collectors are located inside the auma and the heat is transferred to the supply air by a heat exchanger. The heat from the composting operation is thus used to dry the pulp. '·' 'However, the method shown is quite tricky.

It is an object of the present invention to improve the process of the prior art, and in particular to increase the yield of fuel: ': 3j) and its calorific value. Characteristic features of the invention are set forth in the appended claims. The invention is largely based on the finding that the cellular structure of the most difficult to dry organic pulp is rapidly destroyed by composting, which facilitates thermal drying and can interrupt mechanical composting. Composting in mixed sludge is strongly triggered by the use of bio-sludge, 3 108649, which is the most difficult part to handle. For example, the wood fibers of the fiber slurry, on the other hand, last longer and the calorific value of the pulp remains. Other advantages and embodiments of the invention will become apparent below in connection with the examples.

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The invention differs from the method of the aforementioned Swedish publication in that the effective drying step is a separate process only after sufficient pulp has been decomposed. Although the Swedish publication proposes the principle of using compost-10 n heat to dry the pulp, the proposed system is not effective. Apparently, the inventor did not understand the basic idea that the cellular structure of the pulp should be destroyed by vigorous composting before thermal drying. Initially, thermal drying is wasted because capillary and col-15 parasitic water do not, however, escape from intact tissue. On the other hand, in the final stages, composting produces poor heat.

The invention will now be described with reference to the accompanying drawings.

20 Figure 1 shows different options for the drying process • ^ Figure 2 shows the amount of air [and temperature] in the composting and drying process Figure 3 shows a composting plant specializing in drying * ··· * '2 * 5 "· *' As shown in Figure 1, mechanical composting 11 is discontinued after 6-7 days, when it would normally last 10 to 14 days: According to the simplest alternative I, partially composted '... · and eg dried for two days separately:'; '30 is placed outdoors, preferably in a canopy heap, where it is further composted in a little over 2-3 weeks. Storage will in any case equalize moisture throughout the bag !!!, resulting in consistent fuel quality. Mechanical drying reduces the duration of auma drying and weather dependence. with the help of heat and dry outdoor air, the drying continues 41086 The condition in the Aum continues to rise significantly for several weeks. Only the thin surface layer is cooled by the outside air. In summer trials, drying out in the open air and in the barn without a roof occurred within weeks of the target-5 humidity despite the rainy period. Only October-November are often found to be so unfavorable in weather type that dehydration does not occur.

In Option II, the drying is completed by mechanical drying (silicon) (3-4 days at 50% target humidity). This avoids any dependence on weather conditions. Mechanical drying is also necessary if the target fuel humidity is much 50% lower.

The process consists mainly of a normal composting process and an air-intensive drying step. The mixed slurry to be dried is mixed, if necessary, with a support, such as bark or chips, placed in a composting tunnel and composted for 6-7 days, depending on the moisture content. • · · · · · * may not require any support material for mixed sludge composting. One such batch of mixed slurry contained 8500 kg of fiber slurry, 6500 kg of bio slurry and 2000 kg of pasta slurry in the dry matter. In another batch ... *, 0.4 m3 of bark / ton of mixed sludge was used.

'.'25 ·. · · When decomposing is optimized for municipal bio-waste composting, heat generation is optimized here by adjusting the temperature in the process step to about 50 ° C. This is accomplished by adjusting the ratio of recirculated air to heated fresh air. However, the 3P operation is started by raising the temperature of the compost mass i · for a short time to a remarkably high temperature (60-70 ° C), whereby harmful bacteria die. After the composting step, the mass is most preferably dried in the same composting tunnel, which uses the heat 35 produced by composting other sats. The moisture content of the compost mass after the composting stage is 55-65%, and the moisture is reduced to 5-108649 desired, i.e. 45-50%, after drying. After the drying step (3-4 days), the pulp is either directly incinerated or placed in an intermediate storage bin.

As shown in Figure 2, a large amount of circulating air is used in the start-up phase and a large amount of fresh air in the drying stage.

In the method, composting has the following functions: - providing the free energy needed for drying 10 - performing 55-65% initial drying - de-odorizing the sludge - hygienizing the sludge - breaking down the cellular structure (intracellular water) of the organic material, especially the bio-sludge - Reducing harmful nitrogen in post-combustion The benefits of post-drying are: -Using the free energy of composting to reduce 20 composting times and reducing plant size • Ensuring the desired incineration humidity in all situations »· · '· *' The process can produce efficiently and economically • M ~ '···' smelly sludges and other organic masses are fuel. The overall economy is better than, for example, digestion, '' '' ', thermal drying and mechanical drying alone, since drying uses the * energy of the process itself. The process is simple and manageable. The end product can be utilized in existing boilers without any special arrangements to replace conventional fuel purchases. In addition, environmental damage can be effectively managed.

Figure 3 below shows one possible arrangement of plant size-35 with flow diagrams. The tunnel composting plant itself is 108649 6 otherwise conventional but has a more versatile air conditioning system.

The main components of the tunnel composting plant of Figure 3 are, in addition to the composting tunnels 13 provided with an air distribution base 13.1, a scrubber 15 and a biological air purifier 16 for purifying the exhaust gases. In addition, the composting plant 1 includes a versatile air circulation system. The fresh exterior supply air is heated by the scrubber 15 in the heat-to-ion exchanger 17 and supplied to the distribution duct 10. Here, the heated, oxygenated and dry fresh air is optionally fed with recirculated air through 3-way dampers 11 and blowers 12 to air distribution ducts 13.1. These supply air to the mass to be treated, and the air exits, controlled by the other is 3-way valves 14, either to the cold exhaust line 18 'or to the exhaust line 18 to the scrubber 15, from which recirculated air is drawn into the circulating air duct 19.

The air from the scrubber 15 is led to a biological purifier 16, 20 to remove odor-causing compounds from the exhaust air.

The water circulation of the scrubber 15 forms with the heat exchanger 17 a heat recovery apparatus.

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It is of particular importance that the air supply and removal of each composting tunnel 13 *. '2 * 5 can be individually selected and carried out by means of the desired treatment step, 3-way dampers 11 and 14 and fans 12 on the other hand.

»· ',., ΪMM) air leaving the composting process (start-up and process step) has a temperature of 40-60 ° C and a relative humidity of, ··. 100%, so it is not possible to dry with recirculated air. During the drying phase, the exhaust air is so cold that it is no longer useful to recover heat. On the other hand, it does not require any laundry, so that it can be directly led to a biological cleaner 16.

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Part of the airflow from the hot exhaust line 18 is recirculated through the circulating air passage 19 to the selected composting tunnels 13.

5 In Figure 3, the three composting tunnels 13 of the plant are shown to operate at different stages. In most cases, at least two composting tunnels are simultaneously in the process stage. Preferably, the number of compost tunnels is at least four to ensure consistent and efficient heat generation. In Figure 3, 100% recirculated air is fed to the composting tunnel in the start-up phase at high power, whereby the mass warms up and the composting starts quickly. The air is removed to the exhaust line 18. At the very beginning of the start-up, when the exhaust air is completely cold, the exhaust air may be led to the cold exhaust air-duct 18 '. Within 24 hours, composting has started effectively and is moving to the process stage.

In the process step, maximum heat output is maintained, whereby the temperature of the sats is set to about 50 ° C (generally, in the range of 20 ° C to 45 ° C). The amount of air is usually only half of the above, and the adjustment is mainly done by proportioning the amount of fresh air and recirculated air to achieve the target.

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In the drying stage again, a large amount of air is used, which is only t heated and thus dry fresh air, which is capable of absorbing moisture well. Although the temperature of the sats decreases, drying is effective. Cold exhaust air is passed past the scrubber as described above.

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Claims (7)

108649 A process for making fuel from organic materials, in particular sludges and any auxiliary materials, using mechanical composting, which first comprises bringing the organic materials to a dry solids content, generally about 30%, and dividing the mixed and thus pre-dried pulps by mechanical and batch separation. required for effective composting treatment, which are dried by mass composting, each of which is subjected to a first composting process that breaks down the cellular structure of the organic material to allow for thermal drying and reduces humidity 65-55 | after which the heat generated by composting is used to dry the pulps in a separate drying step where the sat-15 is generally dried to about 50%, characterized in that the sats are treated in a tunnel composting plant with at least four composting tunnels (13) The composting and separate drying of each sack is carried out in the same composting tunnel (13) each by directing either fresh air or fresh air or a mixture thereof in an optional proportion to the composting tunnel according to the respective treatment. V '25 Method according to claim 1, characterized in that the heating of the fresh air takes place with the heat obtained from the exhaust air washer (15) V '. Method according to claim 1 or 2, characterized in that the first main step, i.e. mechanical composting * is divided into a short start-up step and a process step,; , · Which, during the start-up phase, raise the temperature of the bag to short II »···, time to 55 ° - 75 °, more preferably 60 ° - 70 °» · · '· t by essentially supplying warm I · *' · '35 and from which, in the process step, both * »·» »» 108649 fresh air and recirculated air are fed to the satin, keeping the temperature substantially constant in the range of 45 'to 55', most preferably at about 50 '. Method according to one of Claims 1 to 3, characterized in that the second main step, i.e. mechanical drying, is carried out by introducing exclusively heated fresh air into the precipitate. A process for the composting of mixed sludge according to any one of claims 1 to 4, wherein the mixed sludge contains a fibrous sludge with a fraction of 35 to 70%, a biological sludge with a proportion of 15 to 45% and any other sludge, characterized in that the mixed sludge is substantially composted less than 10% solids. is 6. A tunnel composting plant for the production of fuel from organic materials and any excipients utilizing mechanical composting, comprising at least four composting tunnels (13) with air conditioning systems, a fresh air supply system with a heating medium (17), an exhaust gas system (15) V. a circulating air system (14, 18,19) for returning the exhaust air back to the composting tunnel (13), characterized in that ·; ·. the air conditioning system of each composting tunnel (13), ···. independently create duct damper means * *, '\ · 25 (11) on the inlet side so that the air supply to each composting tunnel (13) can be switched in an optional relationship between fresh air and recirculated air. Tunnel composting plant according to claim 6, characterized in that the circulating air duct (19) is connected to a main exhaust duct (18) leading to the gas scrubber (15) and includes an auxiliary exhaust duct bypassing the gas scrubber (15). (18 ') and channel dampers (14) for connecting the deaeration of each composting tunnel in an optional relationship with the main and auxiliary outlet ducts * 35 (18, 18'). 10 108649