FI61357B - FOERFARANDE FOER TORKNING AV FAERSKT GRAES OCH LIKNANDE - Google Patents

Description

RSF ^ l [B] (11) KUU.LUTUSJULKA, SU .-. 757 1 j '' υΤίλβΟΝ I NGSSKKI FT c 1 ~ D 'C u- Patent granted 12 07 1902 • au \? (45) '' Fatent nsddelat 'S ^ ^ (51) Ky.lk?/hrt.CL3 F 26 B 3/06 FINLAND —FINLAND (21) PKunttHwlwmu · - Pumcameknlng 83l /?! * (22) Htkemtapilvi - AiwOlcnlngadtg 19.03 ^ .7

^ * (23) AtkupUvl —Gliclghutedag 19.03.7U

(41) Tullut lulktMkil - Bllvtt offmtllg 2U. 09.7H

Patent and Registration Board ....,. .....

_, (44) Date of departure from the date of issue. - 0-1 n-3 flo

Patent · och registerstyrelsen 'Anikin utlsgdoch uti.ikriftcn puWicarad (32) (33) (31) Pyrlatty priority - Begird priority 23-03-73

Norway-Norway (NO) 1199/73 (71) (72) Bernt Ingvaldsen, Solbakken U3, N-3000 Drammen, Norway-Norway (NO) (7U) Berggren Oy Ab (5U) Method for drying fresh grass or the like - Förfarande för The present invention relates to a method for drying high-moisture grass, fresh fodder, seaweed or the like by blowing air as evenly as possible through a stationary, relatively thick mat of desiccant, whereby the air absorbs moisture from the grass in a drying zone. which is shorter than the thickness of the mat and terminates in a drying front where the air is substantially impregnated with moisture and no more drying occurs and which spreads over the mat, first using unheated air and towards the end of the drying cycle using air heated to reduce relative humidity to about $ 35 or below.

It has long been known that artificial drying of fresh grass can produce valuable fodder that can replace any other type of feed fed to livestock, especially cows and sheep. First, the fresh feed is rich in a variety of proteins in an easily digestible form, with a distribution of different protein species being preferred.

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In addition, the content of vitamins and provitamins, especially carotene, is significant. When the drying process is such that the natural protein and carotene content of the grass is maintained, feeding the dried grass keeps the herd in good condition.

Fresh grass fodder can be of particular importance in Norway, where the climate is very suitable for grass production in terms of rainfall, temperature and lighting conditions. Dry grass production can therefore give a higher yield per unit area of land than the cultivation of other fodder crops. This is also due to the fact that when the rainfall is appropriate, it is possible to fertilize more vigorously because the grass is cut several times during the growing season.

Drying fresh grass is cheaper than storing the grass as tank feed. Thus, the feed concentration is higher and the fermentation of the feed is avoided. In addition, the use of acid is eliminated, as is the pollution caused by silage juice. In addition, it should be noted that silage feeding should be avoided when milk is to be used to make quality cheese. Instead of using dried grass, milk has been obtained which is very suitable for making butter and quality cheese.

Despite the above-mentioned strong support for the use of dried grass, the drying of fresh grass has not become widespread so far. This is due to the difficulties involved in carrying out grass drying rationally and economically on a scale suitable for farm management. Fresh grass comprises a relatively large number of leaves and few straws compared to stagnant grass (hay). The dried grass mattress therefore becomes relatively dense and is easily fermented and rotted during storage. To be preserved, fresh grass must be dried up to a moisture content of 12%, whereas hay can withstand up to 20% moisture, especially if it is stored airily. Considering that the moisture content of freshly cut fresh grass is very high, i.e. about 80% by weight, it can be stated that a relatively large amount of water must be removed during drying. In addition, the grass is so short that it cannot be dried in the stems in the same way as hay. Drying is therefore generally carried out by means of heat in plants which are quite expensive, complicated and / or laborious to use and in which the transport of raw grass plays a significant role. A number of different drying devices are known, such as tumble dryers, belt dryers, bucket dryers, etc., in which the product to be dried 3,61357 is usually in circulation. Heat consumption is very high, often 1000 calories and more per kilogram of water evaporated, which corresponds to a consumption of about 4 kWh per kilogram of dried grass. Such high energy consumption is an obstacle to the economical production of dry grass.

As dry air passes through the product to be dried, it cools and absorbs moisture. After passing through a drying zone, which is usually 20-30 cm thick, the drying air contains so much moisture that it can no longer absorb moisture from the grass. The surface to which this drying zone ends may be called the drying front. When the moisture content of the grass is over about 65%, the drying air becomes saturated with moisture and the drying front remains inside the grass bed. Initially, only the innermost zone of the grass, which is 20-30 cm thick, will be dried. As the moisture content of this zone decreases, the drying front moves outwardly through the product to be dried.

A drying method comprising initial drying with unheated air or only slightly heated air, followed by final drying with a somewhat more heated air stream, is more economical than drying with heated air from the beginning.

This is because it is not necessary to reduce the relative humidity of the drying air by heating as long as the humidity of the outside air does not substantially exceed 70% and the water content of the grass is relatively high. However, it has been found that when the moisture content of the grass becomes relatively low at the end of the drying process, drying air with a relative humidity of 30-35% must be used in order to reduce the water content of the grass to about 12% within a reasonable time. Such a reduction in the relative humidity of the air is suitably achieved by heating a certain amount of air. To avoid this requiring too large radiators, the air flow can be reduced during heating.

Norwegian Patent Application No. 135,644, which has become public, proposes a plant for drying fresh grass in several stages using several stationary batches of grass. The plant consisted of a ventilated storage site comprising one or more covered boxes for initial drying with unheated air. The batch of grass was then transferred to a drying device with a hot air circuit to complete the drying so that the storage site could again be filled with a new batch of freshly mowed grass. This batch was initially dried while "61357 the first batch of grass was finally dried in a dryer. Such a method is relatively laborious because all the grass has to be moved from place to place. The plant is relatively large and expensive.

It has also been proposed (see Norwegian Patent Publication No. 108,897) to dry fresh grass in a "drying shed" with a grate sloping floor through which drying air is blown upwards by means of a fan behind the "shed". Such a drying shed is relatively simple and labor-saving. However, it is still a fixed institution.

Moreover, in the above-mentioned plant, it has proved difficult to avoid drying air flowing along the walls without being distributed through the product to be dried. In addition, the heat economy is not permanently satisfactory.

It is therefore an object of the present invention to provide a method which is substantially more economical than previously known methods because the energy consumption per kilo of dried grass is kept as low as about 2 kWh or less, while the method can be carried out using a plant that is simpler and cheaper than known plants. In addition, it is intended to provide a facility that can be easily dismantled and relocated as needed so that it can be used at different locations on the farm, possibly on several farms in a row.

The method according to the invention is characterized in that drying with heated air starts before the drying front has reached the outermost layer of the mat, so that most of the product to be dried, except the outer layer, is pre-dried to the desired moisture content when the drying front reaches the outer surfaces of the mat. the layer is completely dried, in which case the layer which has not yet dried is removed to dry it in a new drying process.

In this way, it can be ensured that the drying capacity of the air is utilized as well as possible, since the grass mattress at all times comprises an outermost layer with a relatively high moisture content. This is especially important in the final stage of drying, when air is used, which has taken up quite a lot of energy in the form of heat and is therefore expensive. The air drying used in the process according to the invention has such a high moisture content that it should not be recycled.

According to another aspect of the invention, two or more mattresses can be dried simultaneously using a phase shift of the drying cycle with heated air such that the total power required to dry the mattresses remains approximately constant. By synchronizing two or more plants in this way, a rational use of a common heating device is achieved, i.e. an economic load on the electricity network without the need to move all the grass.

The plant designed to carry out the method according to the invention has an air duct which leads from the air intake located considerably above the ground and turned away from the grille down to the ground and further horizontally into the deaeration pipe, and a grass-bearing grate comprising down-to-ground That part of the channel which runs along the ground may possibly be embedded in the ground.

The air duct may be divided into sections to facilitate the transfer of the plant. The grille can also be divided into parts that can be joined together to form a self-supporting dome over the deaeration pipe. The location of the air intake well above the ground is advantageous in that it does not suck in air close to the ground, which is often wetter than air above. In particular, this reduces the risk of the used drying air being recycled, because the air passing through the product to be dried, which has a relatively high humidity, has a lower temperature than the ambient air, so that it settles on the ground.

Due to the fact that the grate extends to the ground resting on it, a grass mattress placed on it, suitably 1-1.5 m thick, should also extend to the ground around the grate and provide sufficient sealing so that the drying air does not escape directly, but is distributed mainly through the product to be dried.

The plant may further comprise a cage which also rests on the ground outside the edges of the inclined grate surfaces to limit the mattress of product to be dried and to facilitate the provision of a suitable shape and thickness.

The fan may preferably be located at the outlet end of the air duct so that it will be located under the grille and will be surrounded by grass during use. This investment results in a significant reduction in the noise emitted partly from the plant and partly through the efficient utilization of the heat generated in the fan motor.

The invention will now be explained in more detail with reference to the drawing.

Figure 1 shows quite schematically a plan view of a plant according to the invention.

Figure 2 is a section along the line II-II in Figure 1.

As can be seen from the drawing, the plant comprises a truncated pyramid-shaped grate 1 placed upside down on a fan 2 arranged in the outlet pipe 3 of the duct 4. The fan may also be located some time before the outlet pipe 3 · Both the duct * 1 and the grille 1 rest on a base 5, which may simply have a ground surface. The grating 1 is divided into parts, e.g. four four trapezoidal inclined surfaces 1a - Id and a rectangular upper surface le. The parts can be made of, for example, iron mesh hatches, so that a large flow opening to the air is obtained. The parts can support each other and together form a self-supporting dome delimiting the distribution chamber 6 above the deaeration pipe 3. The deaeration pipes can be given any shape as long as the shape is suitable to ensure an even distribution of air in the distribution chamber. The product to be dried is marked with reference 7 in Fig. 2. It sits tightly against the ground surface 5 due to its weight. In order to prevent the grass mattress from cracking at the upper end of the inclined surfaces la - Id, these surfaces must be in such a gentle position and provide such a high frictional resistance that the grass does not slide down along the inclined surfaces.

In order to provide a suitable distribution and thickness, the grass mattress 7 is provided with a cage 8 arranged around the air distribution chamber 6, which may be formed of hatch-like parts or a collapsible net.

The supply air duct 4 of the fan 2 extends along the ground 5 outside the grass mattress 7 7 61357, where the duct is connected to a vertical air intake duct 9, the air intake opening 10 of which is provided with a control flap 11. A radiator 12 is arranged in the duct 9 and the control flap 13 directs air flow through or through the radiator. The air intake opening 10 is directed away from the grille 1 and is located, as shown in Fig. 2, considerably high above the ground 5. In connection with the duct 9, walls 14 may be arranged to prevent further air escaping through the grass mattress 7 from entering the air intake opening 10.

When using the plant according to the invention, the air duct and any wall 14 are placed on the ground where the connection to the electrical network can be made. The channel 4 can possibly be placed in a ditch dug in the ground. The grille 1 is then assembled over the fan 2, as shown in the drawing. In order to keep the ambient air used for the drying process as dry as possible, the drying plant should not be located in a shady place. The place should be located away from trees, as the air near the trees is often cooler and wetter.

The thick freshly cut grass is taken to the grate at a thickness of 1 1-1.5 m. The grass is positioned so that the airflow resistance will be substantially equal in all directions and the compaction pressure against the ground or substrate will be sufficient.

When the fan motor is placed under the grille 1, the heat generated by the motor and the fan becomes the most used, while the noise caused by the fan, which can be quite embarrassing, is practically avoided. The air duct 4 is made wide and low in shape so that there is enough grass on top of the duct to provide compaction. The air duct may, as mentioned above, possibly be embedded in the ground. The upper side of the duct 4 may have transverse projections or be otherwise made uneven in order to minimize air leakage along the outer surface of the air duct.

During the drying process, the air blown through the grass cools, and when unheated air is used, the air leaving the grass bed 7 is colder and wetter than the surrounding air. The exhausted air therefore tends to land towards the ground. The shown location of the air intake 10 effectively prevents this air from returning to the process.

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As it passes through the air distribution chamber through the grass bed, the air cools and receives more moisture. After passing through a drying zone, usually 20-30 cm thick, the air has such a high moisture content that it can no longer take in more moisture from the grass. If the moisture content of the grass is greater than about 65%, the drying air will be substantially saturated with moisture. Initially, only the inner layer of the grass mattress, which is 20-30 cm thick, dries. As the moisture content in this layer decreases, the drying zone passes through the grass bed.

Air with a temperature of 150C and a relative humidity of 70% can theoretically dry the grass to a water content of up to about 27%. In order to bring the water content of the dried grass to about 12%, air with a relative humidity of less than 42% should be used. In practice, the relative humidity must be between 35-30%, which can be achieved by heating the temperature to 15 ° C and the ambient air with 70% humidity to 27 ~ 30 ° C.

Most of the water in the grass can be removed with unheated air. As mentioned, such air can theoretically dry the grass to a water content of about 27%, which corresponds to about 7.5 kg of residual water from the original water content of about 80 kg, i.e. that about 72.5 kg of water has been removed. At a humidity of 12%, 2.7 kg of water remain from the original water, so that theoretically it is necessary to remove only 4.8 kg of water with heated air.

In order to keep the drying time to a reasonable length and to prevent the drying line from leaving the mattress too early, drying with heated air should start before the water content has been reduced to 27%. Cold air with a temperature of 15 ° C and a humidity of 70% can be used, for example, for 36 hours, followed by 8 hours of 3 ° * 11a heated air (humidity 58%) and 10 hours of 15 ° heated air (30% humidity). This means that heated air is used for a third of the total treatment time. Thus, it is possible to work using three plants according to the invention with the operating steps shifted relative to each other, so that only one plant at a time is operated with heated air. As long as the drying front has not yet fully reached the outer surface of the product to be dried and this is therefore still sufficiently moist, the drying capacity of the heated air will be fully utilized. The drying plant is preferably located outside the vicinity of the meadow. Short-term rain deafness has a small effect on the drying process, as rainwater does not penetrate particularly deep into the grass bed, but drains away or remains in the outermost moist grass layer.

Slight heating of the drying air makes it possible to place the fan inside the drying system. In this case, the heat generated by the fan motor is also used to heat the drying air, while the noise caused by the fan is reduced to a minimum.

When the slope la - Id of the trusses is relatively small, a very even distribution of air in all directions can be achieved, while achieving an effective seal, so that the drying air passes through the product to be dried and is thus used efficiently.

In addition to the above-mentioned advantages, the location of the air intake opening relatively high above the ground provides the advantage that the heating elements 12 do not become covered, which reduces the risk of fire.

For example, the use of three plants in phase shift with respect to each other causes an even load on the electricity grid when using electric heating. If other forms of heating are used, eg a building dryer, this can be used alternately for each of the three plants. Thus, the economy is improved without the need to move the product to be dried. The inherent drying capacity of cold air is fully utilized at all times.

Claims (4)

10 61 357 A method for drying high-moisture grass, fresh fodder, seaweed or similar products by blowing air as evenly as possible through a stationary, relatively thick mat of desiccant, the air absorbing moisture from the grass in a drying zone shorter than the thickness of the mat and ending in drying. , in which the air is essentially saturated with moisture and no more drying takes place, and which spreads over the mat, first using unheated air and towards the end of the drying cycle using air heated to reduce the relative humidity to about 35 i or less, characterized in that the drying with heated air begins before the drying front has reached the outer layer of the mat, so that most of the product to be dried, with the exception of the outer layer, is pre-dried to the desired moisture content when the drying front has reached the outer surfaces of the mat, and that the drying process is stopped before the outermost layer is completely dry, in which case the layer which has not yet dried is removed to dry it in a new drying process. A method according to claim 1, characterized in that two or more carpets are dried simultaneously so that the drying cycle with heated air is phase shifted so that the total power consumption for drying the carpets remains approximately constant. 1. Sätt att torka gräs, grönfoder, täng ochilnodukter med hög fukthalt med möjligast jämnt fördelad genombläsning av luft genom en stationär, relativt tjock matta av torkgods, var-viö upptar fuktighet frän gräset i en t mattans tjocklek och som slutar i en torkfront, där luften är huvudsakligen mättad med fuktighet och torkning ej längre äger rum, och som rör sig ut över Mattan, varvid det först används oupp-värmd luft och mot slutet av tork minskning av dennas relativa fuktighet account ca 35% eller mindre, kännetecknat av att torkningen med uppvärmd luft bör-jar, innan torkfronten kömmit account mattans yttersta skikt, ä att största delen av torkgodset med undantag av det yttersta skiktet