DE2940164A1 - METHOD FOR DRYING AND BURNING SOLID FUELS FROM WATER-BASED ORGANIC MATERIALS - Google Patents

Description

29A0164

PATENT LAWYERS

Dlpl-ing. P. WIRTH ■ Dr. V. SCH M IE D-KOWAR ZIK Dipl mg. G. DANNENBERG Dr. P. WEIN HOLD Dr. D. GUDEL

335024 SIEGFRIEDSTBASSE

TELEPHONE: C089)

SK / SK

Case: 1398

MoDo-Chemetics Aktiebolag

Box 313

89101 örnsköldsvik / Sweden

Process for drying and burning solid fuels from hydrous organic materials .

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The present invention relates to a method for improved energy recovery during drying and incineration solid fuels made from hydrous organic materials. Such materials are e.g. bark, shavings and others Wood waste from saw mills and cellulose pulp mills, peat, sludge from municipal and industrial sewage systems as well as household garbage (sorted garbage).

j ίο In larger industries such as cellulose pulp and paper mills, as well as larger communities are large garbage or. Mud is often a problem; their landfill on garbage dumps can often pose an environmental threat. Other methods of recovering sludge, such as rotting and VerkaDen ("liming") are associated with high costs, which are not brought back in the case of compost formation. because there is little interest in compost as a soil improver. Hence, systems for drainage; and drying sludge for incineration. The SW PS 71 13 295.5 describes a process * for dewatering sludge filter cake. According to this procedure * ι j wJrd Vbuextlsapf blown onto the filter cake to keep the water in!

; it is less viscous and therefore easier to remove

, make, e.g. by means of a vacuum. Obviously the Betriebsj is low ₂₅ economics of this process. Characteristic! for the previously known systems for handling sludge it is that they have high operating costs despite the production of the high combustion heat of the sludge. Furthermore, the effectiveness and reliability in the operation of these systems are not satisfactory. ^:

;

ι Mainly for environmental reasons, bark is currently used extensively as a fuel, since in many places in Sweden it is forbidden to deposit bark. The effectiveness of bark incineration systems is usually low, which is shown by the fact that you have to add oil and burn it, especially in winter, in order to keep the burning of the · ■

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Reach bark in the boiler. If the dryness of the bark is below 30 %, which is often the case, it does not burn; without supporting (additional) fuel. In many> cases the bark is mechanically drained, mostly reached; However, this does not result in a dry content higher than about 40 %. Occasionally the bark is also dried. This is done ί using exhaust gases from a special boiler, in which part of the bark is burned, or by means of; j ίο application of exhaust gases from a steam boiler, in which _f I all bark is burned. Measurements from an installation of the first-mentioned type show that about a third of the bark I j burned separately to dry the remaining two thirds

became. The dried bark then obtained then has a dry content of about 45 % compared to that of! of about 30 % before drying. Considering the j originally available Borkemenge is therefore lost in this process, about 15% of the calorific value, the ι \ would have exploited in a steam boiler Künne be j 20 if it had been possible, the bark with a solids content of 30% with no operating problems to burn. A ; ι drying after two mentioned method is ^economic:; borrowed motivated, aimed at increasing the dry; content by more than 10% and is usually applied only \ 25 to achieve more uniform operating conditions. Will '. If the dry matter content is increased by more than 10 # with the help of exhaust gases j, the overall effectiveness then decreases too much.

ί Bark is usually _{burnt on fire grates, I 30} so-called sloping fire grates (rosts). j Combustion in cyclone ovens is also used. Both devices are relatively expensive and labor-intensive compared, for example, to suspension burning. It is known that lower and the boiler ₃₅ GroE SSER and costly, depending wet the bark of the effectiveness coefficient. the effective heat value of the bark varies with the type of wood and is for Rottannenborke about 10 MJ / kg of dry bark. Rottannenborke '

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of 40 % dry matter has an effective calorific value of _; about 14.5 MJ / kg dry bark. Considering how much the effectiveness of the boiler decreases with the dry content of the material to be burned, it can be stated that the overall effectiveness of the current bark combustion - i.e. a bark with about 40 % dry content - is only insignificantly , significantly above 50 %. lies.

j κι Peat is also currently used to a small extent as an energy source j. The method corresponds to only poorly available I the current demands on a continuous Arbei- • j th, of high reliability and economy. ■ j Peat obtained by cutting is produced in the summer months jj _t5 with a dryness content of no more than 40 to 50 % . ^: \ During rainy periods the peat is wetter, and its warmth.

value decreases quickly with reduced dryness.

In order to achieve a uniform peat production throughout the year, different types of peat treatment ^! I ₂₀ development. The most interesting is what is known as wet coaling, which enables the peat to be mechanically dewatered to a dry content of around 50%. The one in peat; The peat present in moss has different dryness and composition. _{Normally,? 5} has this raw peat has a dry content between 10 and 20 I% and can mechanically without any type of treatment

not easily dehydrated to more than 35 % dryness! will. The wet char means that the peat is heat treated at a concentration of 5 to 10 #. Characterized the suspension I ₃₀ is pumped through a heat exchanger, in which it is heated j, and lung reactor from there into a wet Verkohj in which direct heating with water vapor ί is carried out over a longer period. The treatment is usually carried out batchwise j for a period of 1 to 2 I _T> hours at 150 to 200 ° C. The GB PS 183 180 and the SW PS; 40 679 and 46 995 describe methods and devices for heating the peat suspension by means of steam. While !

j the heat treatment, 1 to 2 t of water vapor per t,

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Dry matter is used, and the water vapor is condensed in the peat suspension or on a heating surface, depending on the type of plant used. During the 5 long wet charring period, the amount of dry matter is reduced by at least 5 to 10 % by oxidation of the organic material in carbon dioxide and water. After the wet charring, the suspension is exchanged for the new peat suspension to be treated, which is thereby preheated i io. This preheating can be done in a

I j

! SW PS 46 386 described device can be carried out. ^{

j After the wet charring, the peat is mechanically pressed [

! dehydrated to a dry matter content of no more than 50 %. A

j large part of the press water thus obtained is again to

j i5 dilution of the peat suspension is used while the remaining

I borrowed press water must be removed. The thus obtained,

moist press cakes made from semi-dry peat are called

j fuel used even if the calorific value of the peat

! is low due to its low dry content. An egg

j _{? 0} further increase in the dry content of peat is just through

! Drying possible. There is currently no economic one

ι drying process. There are peat bricks with one

: Dry content of about 90 %, but this fuel can

j not used industrially due to its high price,

1 2b but preferably used / in households. the

! Frequently used drying processes use exhaust gases

j from burning the fuel as a drying medium.

This means that the dry content of the peat from heat

> not increased by more than 10 96 for economic reasons

i can be 30. When the peat is dried in several stages

! a slightly better effectiveness is achieved. With the so-called,

j Bojner dryer described in SW PS 9837 will do the

^: Material in the air first with moist air or water

i steam as a heating medium and then in exhaust gases from a combustion

J ₃₅ drying oven for the fuel dried. U.S. Patent 2,014

! describes a device in which water vapor is used as

I drying medium is used. In this one, however, the

j Peat first in the air with hot water as the heating medium _; i ·

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ι - ir - I

gwditzt, with the water by washing the damp

Will get air "di · from the steam-heated ^l drying stage in which the peat finally dried

ί> is, originates. It was stated that this procedure despite;

its considerable complexity the heat consumption:

only reduced by about 30 % when drying. Next gives'

there are other special drying methods for peat, such as!

drying in molten metal according to GB PS!

to 183 180. j

The peat is burned in different types of
Boilers. The burning of coarser particles such as Torfpreß- \ cake, is carried out on a type of grate is usually air; from the combustion passed through the grate to dry the peat in the boiler before lighting. Smaller and most importantly; dry peat particles are burned in powder form. That :

! Powder is often used together with the combustion gases in the j! Blower boiler. Burning wet fuel!

j 20 requires a greater excess of air than dry j Fuel, which produces a larger amount of exhaust gases and a lower *

ί Temperature of combustion and exhaust gas results. This leads to, !

'< together with the fact that often a large part of the
ί energy content to evaporate the water content of the moist ■; To get a certain amount of energy
win is therefore more fuel and a bigger and
therefore more expensive boiler than using one
dry fuel necessary. For peat, the effective '30 heat value is around 20 MJ / kg dry peat. In Fig. 1,
shows how the calorific value decreases with an increased humidity quotient. That approximately 3 MJ are necessary for the production of 1 kg of water vapor under the assumption in a \ boiler,
: One can theoretically about 6.7 kg steam per kg of Trocke-J received ₃₅ ner peat. When the peat has a dry content of
ι 50 % , then the effective heat value is as shown in FIG. 1
j can be seen at around 8.5 MJ / kg. Under consideration of ; lower combustion efficiency can be 5.1 kg

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Produce water vapor per kg of dry peat. If it is to be economically viable to dry peat with a dry content of 50% , then no more than 1.6 kg of water vapor per kg of dry peat must be used, which is not possible with current drying methods. With an available pre-treatment process, i.e. wet charring, peat with a dry content of 50 %

: with a water vapor consumption between 1 and 2 kg / kg

j ίο dry peat preserved / oomlt "remains a net production of between 3 and 4 kg per kg of dry peat. Depending on how well the drying is from the thermal economy .

The overall effectiveness is therefore between 3 x 100 / 6.7 ■ 45 % and 4 χ 100 / 6.7 = j

ji5 60 %. This simple equation shows what you are doing ^now?

S according to today's methods when using peat as fuel can gain energy.

j The present invention solves the problem of the improved

j 20 Generating energy from drying and burning solid fuels made of water-holding organic materials such as bark, peat and similar substances.

j Thus, the present invention relates to an encryption: ₂ s pass, wherein the water-containing material of solid "contaminants such as stone and metal, free and Mechai nisch dewatered in one or several stages, and divided optionally in the coarse and / or fine- Form disintegrated ■ and dried and burned in an energy / heat plant 30 and before the final mechanical dewatering directly with; Water vapor from the drying system is heated, with the drying medium consisting of Ubermosphä-ί rischem water vapor and which is characterized in that water vapor, which is formed in the energy / heat system! 35, after passing through one or more! Turbines as an indirect heating medium for the water vapor

j is used in the drying plant. j

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The process has several advantages. It is essential, '■ that the energy that a far more effective to win in water-containing organic materials such as bark, peat, and sewage sludge available ■> 1st than before. By working up the fuel in stages using energy with constantly increasing temperature and optimizing each stage from the energy standpoint, the losses can be kept to a minimum, so that the overall effectiveness is surprisingly high. This also enables | Process according to the invention, the handling of the organic i material in a simple and technically safe manner, j which means that you can build a drying and incineration ι plant that continuously without disruptive under- j

is breaks can be operated. The mate can continue! resources in an environmentally advantageous manner; Way to be recovered. The advantages of the present invention are shown more clearly in the examples, which describe the application possibilities of the method in more detail i

A) practice and illustrate with the help of the drawings.

The method according to the invention is first general and then in detail for the preferred, water-containing, organic materials, reference being made to the drawings 1 to 5.

Fig. 1 of the drawings shows how the effective calorific value with the increased moisture quotient of the peat varies. :

: h) Fig. 2 shows a plant in which the method according to the invention is used for drying and burning peat with a dry content of 10 % .

Fig. 3 shows a system in which the invention \ 3s method for firing and burning a peat having a dry content of 25% is applied.

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Fig. 4 shows a plant in a cellulose pulp factory in which the method according to the invention is applied to bark will.

Fig. 5 shows a plant for drying and incinerating a non-rotting municipal sewage sludge using of the method according to the invention.

ίο If the organic material has solid impurities, such as Contains stones and metal, these are removed in a known manner before the material is treated according to the invention will. Furthermore, it is sometimes necessary to determine the particle size of a certain proportion of the material prior to the invention Decrease treatment. For example, if the organic material is bark it is usually necessary to use the coarsest and disintegrate the largest pieces of bark.

The incoming organic material is mechanically dewatered in one or more stages. The number of dewatering stages depends on the dry content of the added organic material. If this is relatively high, for example 20 % or more, only one dewatering stage can be sufficient. This is the case, for example, when treating peat according to the invention which has already been partially drained and dried in the peat moss. In most cases, however, two or more stages of dewatering are necessary. The dewatering process is carried out with known devices, for example a hydraulic press, screw press, decanter centrifuge, band sieve press or roller press. Before the last mechanical dewatering stage, the organic material is heated with water vapor by water vapor condensing directly on the organic material. This direct water vapor condensation takes place at atmospheric or superatmospheric pressure. The construction of the device used for this pretreatment stage depends on whether it is atmospheric or superatmospheric i

Pressure is applied. The organic material is at \

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Entering this pre-treatment stage have a dry content of at least 10%. In this stage, the dry content of the organic material is temporarily reduced because> water vapor condenses in the material. The temperature of the orga African material during this pretreatment step is usually between 40 to 150 ⁰ C, and the residence time varies from a few minutes to 1 hour, depending on the temperature and the material to be treated. Of the ; The water vapor to be used for direct condensation on the material is obtained as excess water vapor from a later water vapor dryer in the process, ie a dryer in which the transport medium and drying medium are the same, namely water vapor at a pressure above atmospheric. The steam dryer is described in more detail below. Between the pretreatment stage j with direct water vapor condensation on the material and j the real drying stage, the material is subjected to a final mechanical dewatering, for which purpose the already mentioned dewatering device is used; will. Before the material is in the steam dryer the drying! If it is subjected to treatment, it must sometimes be married or disintegrated. Whether or not the material should be disintegrated at this treatment stage is determined in part by the type of material being treated, e.g. peat, bark or sludge, and in part by the type of dewatering equipment used, and to some extent; determined by the construction of the steam dryer. ^: The material can be used in any suitable device, e.g. Hammer mill, needle mill or ball mill, milled or disintegrated. Suitable devices for insertion; of the material in the drying and / or treatment device are devices with rotating blades, screw feeders, screw presses and the like. The design of the steam dryer can vary widely. However, all dryers used have in common that the drying system is closed, so that an over-atmospheric pressure is maintained,

the height of which can vary, but at least 1 MPa (10 bar); must be. If the organic material consists of bark or peat, the dryer is designed to take heat

^{5 is transferred} from the water vapor to the material by convection. If the organic material from the mud, \ then the dryer constructed so that the heat is transmitted through large-j tenteil line (conduction). In the former case, the drying system contains a valve

'»Lator, which the water vapor and the material around the system ι around dries, a heat exchanger and a cyclone device. To the heat exchanger w; | .rd_das drying and j

j Transport medium, i.e. the "carrying * / water vapor, with all

heat required to dry the material is supplied;

15 by using water vapor at a higher pressure and temperature.

I rature indirectly in contact with the "supporting" water vapor j

j brings. The heating water steam comes from a turbine. These '

j is in turn with steam e from a steam boiler \

j charged, in which the water vapor by burning the>

J 20 dried material and, if necessary, additional

; iron fuel, like oil, is formed. In the cyclone

; direction, the dried material is removed from the "load-bearing"

i separated water vapor, which continues its circulation

j and partly, as described above, for pretreatment

;? b stage is directed. ;

j in the bottom of the cyclone device there is a device

tung that the dried material in the atmospheric

! Pressure releases and the wings ("vane") from a $ ¥ jhS ^ i bind

| 3o or screw insertion device. The drying

j of the material takes place during its transport through the

j Drying system, i.e. the water in the material is connected

I ßend converted into water vapor on the way of transport. There-

i through excess water vapor is formed in the dryer,

i 35 whereby you get a certain amount of water vapor continuously

] can be withdrawn from the drying system. The drying system

j can also comprise a fluidized bed in which the material

j is held for a certain time before it is due to his

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due to the drying of reduced weight absorbed by the water vapor and to the remaining section of the drying; system is continued. When drying sludge, a so-called contact dryer is used, in which the heat; is transmitted by conduction. In this case, too
the indirectly heating water vapor is obtained from a ι turbine. !

S ίο After drying and running, the material is removed from the drying j

system usually by means of a fan to the furnace '

, a steam boiler for the purpose of combustion. As j

j Air and / or exhaust gases are used as the transport medium. In \ j this transport the material is further j by means of a so-called. \ I5 freeze-drying (flash freezing) dried. If the mate-!

j rial is fed into the steam boiler for combustion, i

I should have a dry content of over 90 % . Next should '

j the particle size of the material when burning is less than 3 mm,!

j are preferably less than 1 mm. If the particle size \

J ₂₀ exceeds this level, the material must be taken out after delivery;

j the drying device and grind before burning j

i or be disintegrated. This can be done, for example, in a so-called Kramer mill. The two conditions, namely one
. Dry content above 90 % and a particle size below 3 mm,
' _{? b} lead to the fact that the combustion is as complete as possible with

: there is a low dust content in the exhaust gases, and therefore '

. also the amount of exhaust gas is low, which is a small and therefore ^:

cheap steam boiler means. Next is this one I

i professional and safe in operation. The one in the steam boiler

30 burning the dried material formed water vapor
I is, as already described, to a or given

I if led to multiple turbines. Pressure and temperature

; of the water vapor are to be found on arrival at the turbine (s)

! ne (n) very high, e.g. 11.5 MPa (115 bar) or 53O ° C. One
J _3S significant amount of this energy is generated by means of an or
converted into electricity by several generators. If the
Pressure of the water vapor to about 1 to 2 MPA (10 to 20 bar)
has sunk, part of the water vapor is used;

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as an indirect heating medium for the drying and transport water vapor, as already described. The water vapor of lower \

> Pressure can be used for a variety of purposes. E.g.

locally
can power through in a / remote heat exchanger; Production of hot water obtained for other heating purposes; will. Should the remaining steam be used as process steam, e.g. in the cellulose industry \

ί

in, then its pressure should be appropriate to that in the drying plant pressure used, i.e. 0.3 to 0.6 MPa (3 to 6 bar).

The following examples illustrate the present! is invention.

Example 1,:

Fig. 2 shows a plant in which the method according to the invention is used for drying raw peat and its subsequent combustion. _}

The Torfsuspension1 with a dry content of 10% is preheated in a heat exchanger provided with scrapers 2 \. The scrapers keep the heating surface clean and result in thorough mixing of the peat suspension. This _; ■ 25 is in the heat exchanger 2 with press water of a temperature; from about 65 ⁰ C, which comes from the following two dehydration stages, preheated to about 50 ° C. The first dewatering of the peat suspension takes place in a dewatering press 3 at a maximum pressure of about 2.0 MPa (20 bar). As a result, the dry content of the peat suspension is increased to 35 % . The squeezed out water is collected in a funnel 4 and passed through line 5 to a conventional discharge line 6. The drained peat is led through a screw 7 ί to a pressure vessel 8, which is provided with supports' | _3B is. In the vessel 8, the peat is treated with saturated steam at a pressure of 0.5 MPa (5 bar) for 30 minutes! delt. By also serving as a feed screw; j screw press 9, the peat is again placed on a drying

,

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content of 50 Ji dehydrated and at the same time introduced into a drying device 10. That in the screw press
9 expressed water is collected in a funnel 11
and through line 12 to the usual discharge line 6

guided. Superheated steam circulates in the dryer 10
at a pressure of 0.5 MPa (5 bar), this pressure being the same as in the pressure vessel 8. The water vapor is both a drying and a transport medium for the peat. The J

Fan 13 finely disintegrated peat particles are j

]

by means of the fan in a power drying channel for!

Cyclone device 14 out. The practically water saturated j serdampf is separated from the peat, and a overheating) zer 15, in which heat is indirectly transferred to the water vapor Übergeis is circulated again. The superheat is removed from \ a steam (15 bar) is condensed at a pressure of 1.5 MPa 'and of excess water vapor from
the turbine 16 of the system consists. The discharge steam is transported to the superheater 15 through a steam line 17. The excess water vapor formed during the drying of the peat is separated off! and led through the connecting line 18 to the pressure vessel 8. i

! Ä

■? S After steam drying, the peat has a drying; j stops at 80 % and is stopped by the transport screw 19
j atmospheric pressure and pneumatically transported through line 20 to the boiler 21. During this delivery
j and the transport, the peat is partly due to the pressure drop partly due to the convection in the transport line
! further dried. Before burning, the peat is in

a special hammer mill, which is provided with fixed hammers (Krämer mill), grind 22 together with circulating exhaust gases and then blow them into the boiler as dust. ' _{3 &} When entering the fireplace, the dry content i of the peat is about 98 %. In the boiler 21, which works with a closed feed water system, superheated water vapor with a pressure of 11.5 MPa (115 bar) and ■

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formed at a temperature of 53O ° C. The water vapor is passed through line 23 to one or more turbines 16, the electrical energy to form a generator '-> are connected. Turbine 16 becomes part of the water! steam is withdrawn and transported to the aforementioned superheater in order to superheat the water vapor used as the drying medium. The remaining water vapor is; from turbine 16 at a temperature of 105 ^° C. through line κ »25 and into a separate heat condenser 26. condensed. Other duties of the turbine, which in most ter-I way in the boiler, etc., comparable between the superheaters turns' were, were not represented. The condensed feed water is from the acidified heat condenser ji5 26 through line 27 to the boiler and through line 28 out of the

■ Superheater 15 led.

i;

I The following table shows a. Comparison between the after

! the method according to the invention and according to a known <

i? o Process for the production of peat press cake after the wet

■ Energy obtained by charring process. Which focus on the Numbers relating to known methods come from one

ι Process in which peat with a dry content of 8 %

> is preheated in countercurrent in a heat exchanger,

| 25 in which the heat is partly extracted from the already treated, i.e. wet-charred peat is taken. The remaining energy required for preheating is in the form of fresh

> Water vapor added from the boiler. After preheating

j the peat was led to the wet charring reactor, in which

; _3Ü chem the temperature 190 ⁰ C and the water vapor pressure 13 bar

I cheated. The water vapor was released during the 1.5 hour

j permanent treatment in the form of fresh steam

'added. After the wet charring stage, the peat was im

I transported countercurrent to freshly introduced peat and

| 3S then in a plate _{filter press to a dry content}

\ pressed by 49 %. The press cakes thus obtained were then burned in a boiler.

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Table 1

Proceed according to required wet charring

theoretical effect content
of raw peat for 10 kg of dry peat / sec; MW 200 200

—— 20th - 29 17th « 19.5 15.5 86 80 168 124 54 33 97 42

Net heat demand
in the preheater; MW in wet char; MW ¹⁰ in the steam dryer; MW

Thermal value of the peat when introduced into the boiler MJ / kg dry peat

Boller effectiveness; % Boller effectiveness; MW

in the form of electricity; MW

in the form of separate heat; MW

As can be seen from the table above, the method according to the invention is obtained in comparison with the so-called wet char;

_Pn regulatory procedure i

(168-124) 100 (

124

i.e. 35 # more total energy, and the increase in terms of generated electrical energy was'

(54-33) 100 _ 63 Ji '·

p, 33 "* ^l

Example 2

Fig. 3 shows another plant for drying and burning! of peat by the method according to the invention. ! 30

j The peat is drained and treated in the peat moss to a dry j content of 25 % , which reduces its transport costs from the peat moss to the plant shown in the drawing. The peat 29 is thus fed to the vessel 30 with a dry content of 25 % , in which it is treated with a steam supplied through line 31 at practically atmospheric pressure (1.15 bar),

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whereby it receives a temperature of 95 ^{° C.} The peat is turned from the vessel 30i via a dispensing device 32 into one
Roller press 33 transported, in which it is dewatered to a dry content of 37%. The squeezed out water is discharged through line 34. The peat web from the roller press is disintegrated into small particles by means of the disintegrator 35, which are then fed to the drying device 36 ^! j be; this contains a fluidized bed through which exceeds j superheater steam (150 ⁰ C) ΐ means of a fan 37, is passed. The superheated steam is passed from the superheater 38 through line 39. In the fluidized bed of the drying device 36, the peat particles are dried, and if they are dry precisely and therefore light enough,. 'they become one with the water vapor from the fluidized bed; • Cyclone device 40 pulled. In this there is a rough; Separation so that the water vapor leaves the upper part of the device and the peat leaves the lower part of the same. Steam and remaining peat particles are fed to a Multi-J ₂₀ cyclone unit 41, in which a final
j Separation of peat and water vapor takes place. This part of the i; dried peat is through line 42 to the lower part
the cyclone device 40 out, where he with the rest
Peat mixed and fed through a feeder
_{Ά is} guided with rotating blades 43 to line 44, the
is in communication with the combustion boiler 45. On leaving the cyclone device 40, the peat has a dry content of 75 %. The exhaust gases are removed from the boiler 45 and passed in line 46 to fan 47, which they
_3o so that the peat is drawn into the boiler,
where the incineration takes place. During this pneumatic
Transportes the dry content of the peat of 75 %
92 % increased. In the boiler, superheated water vapor is released from
high pressure (11.5 MPa) formed through line 48 too
one or more turbines 49 is performed, which are connected to a generator 50 for the formation of electrical energy. A part of the water vapor is removed from turbine 49 at a pressure of 1 MPa and passed through line 51 to the aforementioned superheater 38 to use as a drying medium

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used to bring steam to the superheater. This steam drying medium is over the fan 37 in one cycle through the drying device 36, the cyclone device 40, the multi-cyclone unit 41, the superheater 38 and the line 39 and has a pressure of 0.115 MPa (1.15 bar). The water vapor is removed in this cycle and passed through line 31 to the peat arriving in vessel 30, like this has already been described above. The water vapor removed from the turbine 49 becomes water in the superheater 38 condenses, and the condensed water is through line 52! transported back to the boiler. The rest of the water vapor from turbine 49 Is fed through line 53 to a suitable consumption.

This application of the method according to the invention results in the same high energy production from peat as in Example 1, ie an increased energy production of 35 % in comparison! 20 on the wet charring process.

Example 3. ]

In Fig. 4, a plant in a cellulose pulp factory is shown, in which the inventive method on bark is applied. .

Red fir bark 54, in which the coarsest bark particles had been crushed in a mill (not shown), is fed to a hydraulic press 55, at the entrance of which the bark has a dryness of 30 % and in which it is dewatered to a dryness of 36% . Then, the bark is passed via a transport screw 56 to the pressure vessel 57, in which the j through line 58 introduced water vapor condenses (bar 4) on the bark at a pressure of j 0.4 MPa, whereby the bark is heated to 140 ⁰ C. . The dwell time of the bark in the pressure vessel 57 ^; is 3 minutes. The bark is by means of a Beschik-! Kungsvorrichtung with rotating blades 60 led to loading screw 61, in which they simultaneously j

! J

! __._ _ P.3P..PJ..7 / 0 712 _ i

29A0164

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with their introduction into a closed drying system,
in which superheater water vapor circulates, on one
Dry content of 47.7 % is dewatered. The bark part

Chen fall out of the screw 61 downwards
a mill 62 at the bottom of the dryer 63 and become so
grind fine particles so that the transport water vapor introduced through line 64 can carry them away. Then j pass the transport water vapor and the finely divided |

"Bark a superheater 65» in the excess water vapor from turbine 66 through lines 67 and 68 'and condensed at a pressure of 1.6 MPa (16 bar). Then } transport water vapor and bark are transported through line 70; part of a fan / routed to the cyclone device 71,!

in which the dried bark is separated from the water vapor, ί The bark is removed from the cyclone device by means of a loading device i with rotating blades 72 and passed through line 75 to a further line 74 j, at the end of which there is a fan 75, I through which the finely divided bark (particle size less than 0.4 mm) together with part of the combustion gas and certain other gases are blown tangentially into the furnace 76 ^! will. At the entrance to the fireplace there is bark powder
a dry content of 90 96. The one in the cyclone device!

71 separated water vapor is passed through line 64 to dryer j 63 and introduced into it near the disintegration device, i.e. mill 62. From the return | line 64 is steam partially through line 77 to: steam reforming device 78 and partially through

Line 58 to pressure vessel 57 is removed in the manner described above j. In the steam reforming device 78 is; Water vapor introduced to the bottom, ie on the side of the heat exchanger installed in device 78
Impurities present in the water vapor, such as inert gases, turpentines, acids, etc., are drained from the head and passed through line 79 to fan 75, which they continue to
Directs combustion into the boiler. The condensate from the! Water vapor is from device 78 through line 80;

030017/0712!

Discharged to the evaporation plant of the digestion liquor of the factory, whereupon the evaporation residue is then burned in the soda boiler. To press water line 80 '■> is fed from the feed screw 61 through line 81 and from the hydraulic press 55 through line 82. Aich. On the other side of the heat exchanger in the reformer 78, the feed water received from the plant and supplied through lines 83 and 84 circulates. j io The feed water evaporates at a pressure of 0.4 MPa (4 bar) and the water vapor is carried through line 86 to the factory for use there. The water vapor condensed in superheater 65 is passed through line 85 and mixed in line 83 with the feed water introduced into boiler 76. When the dried bark is burned in the boiler 76, superheated water vapor at high pressure is formed, which is conducted through line 88 to one or more turbines 66 which are connected to a generator 89 for generating electrical energy. From the turbine, water vapor is transported through line 67 at a pressure of 1.6 MPa and divided into two streams. A portion thereof is passed through line 68 to superheater 65 to the indirect heat transfer for the transport of water vapor in the drying system while the other _part?) Line 90 is passed for use in the factory by. The water vapor remaining in the turbine 66, ie after it has been given off and converted into electrical energy, is conducted at a pressure of 0.4 MPa through line 87 to line 86, which is connected to the factory.

In order to investigate the importance of the pretreatment of the bark in the pressure vessel 57, two tests were carried out in addition to the above procedure. In one, the steam treatment in the pressure vessel 57 was omitted; in the other the bark in the pressure vessel with steam at a temperature of 105 ° C, in contrast to the above-mentioned water vapor temperature was treated door of 140 ⁰ C. After passing through the loading screw 61, the dry content of the bark was also increased

JDJLOJDJ. 7 /_0_7_.12.._ _.._ - - -J

25th

i30 ί 35

35 ,8th 36.0 32 , 5 31.4 43 , 0 47.7

measured the following results.

Table 2

Dry without adding v. Addition of 105 ° C addition of v. j salary; Water vapor in water vapor to 140 C water] pressure vessel 57 pressure vessel 57 steam to vessel 57 I

Dry content; %

after press 55 36.3

after steam treatment

after loading screw 61 38.5

As can be seen from Table 2, the pretreatment according to the invention of the bark, i.e. its direct heating, also occurs Steam, to a significantly higher dry content of the bark after the second pressing than without the addition of steam. Even if the energy value of the added water vapor when calculating the energy gain in the invention Procedure is withdrawn, the pretreatment stage still gives a positive result.

If the method according to the invention for drying and burning bark according to the above information is compared with the usual treatment of the same, ie its mechanical dewatering by pressing to a dry content of 40 % and the subsequent combustion in a boiler provided with an inclined grate, then this is Price of the steam produced according to the invention is 35 % lower than that for the usual treatment of the bark. This also applies in spite of the fact that the device shown in FIG. 4 combined with the steam boiler leads to higher investment costs and to a certain increase in the operating costs compared to the usual handling. The lower production costs per ton of water vapor are based on the fact that, according to the invention, a significantly larger amount of water vapor is obtained from the same amount of bark than with the known method. Furthermore, i the method according to the invention enables a simpler and cheaper one; Construction of the steam boiler itself, which also i

_Q.3..00_1 7 / _Q7.12 i

-2?

is more reliable than e.g. a steam boiler with an inclined grate. Due to the improved burning of the bark of about 180 mg / normal m (Nm) exhaust gas in the case of water vapor «

■ χ Ι

Boilers with an inclined grate to about 40 mg / Nm exhaust gases at the j method according to the invention reduced. Another advantage!

a closed system according to FIG. 4 is that the release of oxygen-consuming substances due to evaporation of the condensate from the steam reforming device 78, the press water from the hydraulic press 55 and the press water from the

Feed screw 61 is low.

Example 4

In Fig. 5, a system for drying and burning a non-rotted municipal sewage sludge is below

Use of the method according to the invention shown.

The sludge 91 comes from an activated sludge plant. and has a dry content of 4 %; it is dewatered in a conventional press 92 to a dry content of 10 % . The press 92 can be replaced by a decanter centrifuge, for example. The pre-dewatered sludge is fed to a 'container 93 in which it (the is obtained from a subsequent drying device 94) by direct condensation of water vapor is heated to 80 ⁰ C. The water vapor is transported from the dryer through lines 95 and 96; as it condenses in the sludge, malodorous gases are released which are collected at the top of container 93 and passed through line 97 to a steam boiler 98, in which the gases are burned together with dried sludge and UI. Then the sludge is fed to a band screen press 99 and dewatered to a dry content of 37%. The water squeezed out on the belt sieve press 99 is returned to the activated sludge system together with the water squeezed out from the press 92 through line 100. After the final mechanical dewatering, the sludge is fed to the drying device 94 mentioned above. ,

0 3.0 OJ7_./JL7JL2— '

This consists of a pressure vessel with three axially arranged transport screws, which are designed so that they clean each other during rotation and as pressure-tight locks when loading and removing the sludge serve to or from the drying device 94. warmth is indirectly to the drying device 94 by drawing off water vapor at a pressure of 0.9 MPa (9 bar) ι turbine 102 and transport through line 103 to the hollow; OK transport screws in which the water vapor condenses is added. Part of the water vapor in line 103 is fed via line 104 to the jacket of the pressure vessel, I where the water vapor is condensed. The pressure of the water! steam in the drying device 94, i.e. wb the sludge i15 is maintained, amount to 0.2 MPa (2 bar). In such a It is the drying device called contact dryer

^{: It is} essential that there is good heat conduction between the screws; and the mud is reached. When removed from the! In the drying device 94, the sludge has a dry content j 20 of 90 %; it is released as a finely divided powder and: by means of a fan 105 through line 106 to a cyclone device 107, in which the powdery sludge is separated and passed through line 108 to the furnace i of the steam boiler 98. In the steam boiler 98 the sludge is burned together with Ul; in the

Boiler 98 is superheated steam from high pressure gej forms, which through line 109 to one or more turbines

102, which are connected to a generator to generate electrical energy. Like fishing in the past give, the water vapor is withdrawn from turbine 102 and

led as indirectly heating steam through line 103 and • 104 to the drying device 94. The j in the turbine after removal and conversion into electrical energy i remaining water vapor is passed through line 111 to a _ge -I ₃₅ secreted heat condenser 112, where it condenses. j The condensate is returned to the steam boiler 98 as feed water through line 113. A part of the water vapor obtained in the drying device 94 is, as in j

030017/0712

already mentioned, led through lines 95 and 96 to the pretreatment tank 93. The rest, in drying device
94 water vapor is extracted through line 115 to the (nichjt

& shown) active sludge plant. The sewage comes into this system, which among other things contains certain pools
in contact with active sludge and air. In order to achieve a high growth rate of the sludge in the basin, j the air is heated with the extracted water vapor, j

to which one also achieves an increased temperature of the water in the j basins. '

As can be seen from the above description, the boiler; Ul added and treated together with the dried sludge;

is burning. Since the dry content of the sludge is very j is low and depends on the physical structure of the sludge, it is not possible to dry the sludge ί and then to gain so much energy during the incineration that this is sufficient for the entire sludge treatment.

enough, but one must always add energy from outside, which usually _t in the form of oil happens. As a result, the j sludge treatment was always associated with costs. In dependence of the type I speed of the sludge and its dry content * is between 0.5 to 1, kg of oil o / kg dry sludge in a UbIi- chen method j for drying and burning necessary. In the case of j investigation of the costs for a standard sludge treatment,
eg from dewatering the same in a decanter centrifuge
and drying and burning in a multi-stage oven as well
Ash separation is found to be about 500 SwKr

m per t dry sludge. When treating the sludge
according to the method shown in FIG. 5, ie according to the invention, it has been shown that these costs are reduced by 25%
can be. According to the invention continue to be the levy
bad smells avoided and the problem of not burning

reduced dust. *

030017/0712

Claims (1)

patent claims 1J method for drying and burning solid fuels made of water-based, organic materials such as bark, peat, etc. for improved energy use which removes solid impurities such as stones and metal from the water-containing material, in an or mechanically dehydrated in several stages and, if necessary, disintegrated into coarse and / or finely divided particles, j dried and burned in an energy / helz system; 10 and before the final mechanical dewatering directly i I 'i j is heated with steam from the drying system, in! which the drying medium consists of superatmospheric water There is steam, characterized in that water vapor, i which is formed in the energy / heat system, according to Durchi Is passage through one or more turbines as indirect heating * medium for the water vapor in the drying system is turned. ; 2.- The method according to claim 1, characterized in that ¹ the dry content of the organic material is brought to over 10% in direct 2o heating with steam. j 3.- The method according to claim 1 and 2, characterized in that ί that the organic material after the final mechani-I see drainage being disintegrated. ' 4. - Method according to claim 1 to 3 »characterized! j that the organic material disintegrates finely after drying! is grated. 30. 5.- The method according to claim 1 to 4, characterized in that the organic material is dried to such an extent that the dry matter content is over 90 % during combustion. j 6, - Method according to claims 1 to 5 »characterized thereby- · j i ; ₃₅ net that the organic material is disintegrated to a particle size of less than 3 mm, preferably less than 1 mm, before incineration. L 030017/0712 ORlGiNAL!, \ BrcüTED 7.- The method according to claim 1 to 6, characterized in that the heat in the drying system by means of convection is transferred when the organic material consists of bark or peat. 8.- The method according to claim 1 to 6, characterized in that the heat in the drying system is substantially transmitted by conduction when the organic material consists of sludge. j ίο The patent attorney: 030017/0712