CS221911B2 - Method of valuation of less valuable fuel - Google Patents

Abstract

Upgrading of low-grade solid fuel fines with a particle size of 25 mm is carried out by shaping the fines into coherent bodies and heating the bodies at 150-375 degrees C in the presence of H2O at a pressure higher than the vapour pressure of H2O at the applied temp. The process is capable of increasing the calorific value and mechanical strength of solid fuels (esp. brown coal) with a particle size unsuitable for conventional fixed-bed treatment (cf. US 1632829).

Description

The present invention relates to a method for recovering a less valuable fuel having a particle size of less than 25 mm.

Preferably, the solid fuel containing more than 10% by weight and especially more than 40% of the mono -ootic bound and / or unbound water (hereinafter referred to as less valuable fuel) may be subjected to thermal recovery. This fuel is referred to as less valuable because its weak or friable consistency makes it difficult to control and because the thermal value is too low compared to a commonly used fuel such as anthracite or oil. T Such fuel fuels are young coal (such as lignite), peat, lignite, wood and carbon-containing waste (such as kommpost.

. The young coal, for example, usually contains 40 to 70% of the water and the peat contains 80 to 90% of the water. Water in such fuels occurs in a variety of forms, and in particular as inherent or absorbed water, as a component in combined organic substances (e.g., crystalline water). and as potentially present - water, that is, water that is produced. from chemically bound oxygen and hydrogen during fuel recovery.

It is desirable that these types of water be removed to the desired percentage and separated from the fuel, and hence the thermal value, and the possibility of rejuvenation is improved. Such fuel conditioning results in lower transportation costs and improved burning properties.

There are different ways to make the fuel less valuable and the process used is heat recovery. Examples of various οο ^ ο ^ ί achievement of heat recovery include:

The fuel can be dried (by heating at 10 ° C to a temperature below 150 ° C). As a result, the inherent and absorbed water is driven off and the process requires relatively low energy (heat to evaporate) and in most cases causes only a partial reduction in the water content of the fuel. Typically, the water will be re-absorbed over time.

The fuel can be heated to such a degree of heat (usually between 150 ° C and 250 ° C) that ¹ heat recovery occurs. As a result, chemically bound water is eliminated from the fuel and cannot be absorbed again. This thermal recovery can be carried out under conditions in which the water to be removed evaporates (and this requires additional energy in the form of evaporative heat) or at such a pressure that the water remains liquid (thus physical separation of the solid and liquid phases is necessary). ·

The process may result in drastic conditions under which organic substances, such as salts, salts and esters, are partially decomposed, such as in the case of decarboxylation (carbon dioxide is separated). An organic compound (e.g., R-COOH) of an oxygen group (e.g., a carboxyl group of formula COOH) can de-carbonate, wherein hydrogen binds the remainder of the carbon chain (e.g., according to the equation R-COOH → RH + CO ₂ ). This decomposition takes place at higher temperatures - particularly at 350 ° C - and is associated with drastic structural changes in fuel. For example, carboxylation causes the fuel to become a hydrophobic site because decarboxylation causes the cleavage of polar oxygen groups that have given the fuel its hydro-tilting character.

The advantage of heat recovery in water addition (at txa ^ at higher also the water vapor pressure at the selected temperature) is that due to the fuel gas (most often as a result of decarboxylation) it starts at 300 ° C, while under dry conditions ( at a pressure lower than the water vapor pressure at the selected temperature) the formation of gas at a temperature below 400 ° C is completely insignificant.

In the last series of proposals, an economically acceptable evaluation has been submitted, and the applicant himself has also proposed a procedure of the type mentioned in the introductory part (see British Patent Specification No. 1,471,949). In this slurry-type process, the finely divided fuel is mixed with water and a finely divided suspension and the suspension is heated at elevated pressure until recovery. In addition to a number of advantages, the suspension process has the inherent disadvantage that the added amount of water must also be heated. Nevertheless, the process attracts wide interest from various places.

The present invention does not relate to the above suspension process, but is a fixed bed process that has been known for some time and wherein fuel that does not reside in a pump suspension but substantially without added water is heated in a solid bed. under such conditions that the water to be removed remains liquid. In this description, solid-type processes are included. all processes in which the solid fuel charge or the continuous solid fuel stream is heated without first converting it into a pumpable suspension in water. Such processes may, for example, employ solid, polyhydric or fluidized beds.

An example of such a fixed bed process is a process which basically consists in heating a certain amount of fuel in a container (see US Patent 1,632,829, filed Dec. 19, 1930). No. 12, pp. 1347-13560). The fuel is present in a fixed bed and is introduced by introducing saturated steam into the vessel where the steam partially condenses. The condensed steam and water formed from the fuel passes through the fixed bed and is discharged from the bottom of the vessel. This procedure is widely used in practice. The present invention relates to a process in which, on the one hand, the liquid water is more or less a target during heating and, on the other hand, the amount of water required is low enough that the heated dose is in a solid state.

In the solid state process, the fuel in the reactive reactor must be as uniform as possible in the size of the particles set at a certain upper limit by the requirement that the period of time be sufficiently short that is, the interior of the largest particles must be able to lie at the desired temperature sufficiently quickly to provide a cost-effective process. The lower limit is given by the requirement not to reduce the particles - not to be carried away from the bed and tkutlčnocsϊ that the inherent moisture content increases with the percentage of small fuel particles (the outflow from the bed deteriorates).

Some fuels are available with a small particle size and are not suitable for the process. Other fuels contain fractions, often numerous, of too large a fraction. Reducing them (for example by grinding or crushing) always results in the addition of a usable fraction to a fine fraction with too small particles, which has not yet been used in the fixed bed process. Obviously, these fine particles represent a loss, so they will benefit considerably less than the recovered fuel.

SUMMARY OF THE INVENTION It is an object of the present invention to change this state and the fixed bed process for recovering fine fuel subassemblies.

It is an object of the present invention to provide a method of utilizing less valuable fuel, which is in the form of fine particles of greater than 25 mm, in which the fuel is heated to a temperature of 15/375 ° C in the night of water. than the water vapor pressure at a temperature, characterized in that the fine particles are first formed into cohesive particles before being subjected to a heat treatment and then the cohesive particles are thermally treated.

It has been found that the cohesive particles produce their original strength during heat recovery and often also result in a significant increase in strength. A possible explanation for this is that during the recovery process a certain amount of tar is formed which can act as a binder. In particular, the particles change a certain minimum of the raw strength before the heat treatment so that the moieties can be introduced without disintegrating,. to a device in which it is subjected to heat treatment.

A very important advantage of the process according to the invention is that separating the recovered fuel and separating the water is much simpler and less expensive and that the recovered end product is obtained in conventional form and not as dust.

When practical embodiment it has been found that certain minimum required 'raw strength may be achieved post-dou ^p s. thatch may e.g. ^ Lad gain ^and vat ranging, briketizací, Haeem (production of tablets) and důkladiým slšoováním (upsetting).

A very attractive method in which the shaping of the particles can be combined with introducing them into the space in which the recovery operation is carried out is to introduce fine particles into the recovery space through a staking press or a solids pump to overcome the high pressure.

The pressure to be used for molding the particles remains outside the jink on the fuel type, but usually a pressure of between 10 to 2500 kPa and preferably between 100 and 1500 kPa is used.

Although higher pressures will be correspondingly more expensive, they often provide the advantage of greater strength and the possibility of partial dewatering when forming the particles.

. According to the invention, it is advantageous to shape particles having a maximum dimension of between 10 and 150 mm. On the one hand, such particles coincide sufficiently quickly and, on the other hand, their presence does not cause problems in separating the resulting water from the water. It is preferred that, during particle seizing, the non-homogeneous fines have a particle size of less than 5 mm and preferably less than 10. . mm.

In this regard, it is noted that in all cases the particles will be larger than the particles of which they are composed, so that a lower limit of 10 mm is only applied to particles made of particles smaller in size. t ^ i.

Jessie's raw strength is not satisfactory. according to the invention, a binder may be added to the fine particles before they are formed. Examples of such bands are biumene, oil fraction residues and coal tar,

The principle known per se can be advantageously used in the process according to the invention. According to this, after the particles have been heated and the liquid water has been removed, the pressure in the recovery space is reduced and / or the temperature is increased to form steam, accelerating (ΙΙΙ γΜχ / Ιι) and facilitating the separation of fuel and water. the recovery process continues under modified conditions.

The invention is further elucidated by two particular examples of the process of the invention.

Example 1.

Certain ^ κ ^ β ^ ί brown coal Victors! (Australian lignite with a water content of 53.9% tamonoid and a heat value of 12,887 J / g) is compressed at a pressure of 500 kPa to form a pad shaped tablet having a maximum diameter of 11.4 mm. .

553.8 g of tablets were blended at 250 ° C for 60 minutes under a pressure of 4.5 MPa. During mixing, the tablet remains in contact with the separated water, which remains liquid (the water vapor pressure at 250 ° C is approximately 4 MPa). The resulting water is then drained.

Thereafter, the tablets were heated at 360 ° C for 60 minutes at 40 psi; during this treatment, all the water present and all the separated water formed is in a vapor state (water vapor pressure at 360 ° C is approximately 19 MPah

During both processing, the tablets remain intact, but the desired shrinkage occurs. After processing, the tablets are reduced to only 37% of their original volume (the largest tablet diameter is 8.2 mnb).

It may therefore be noted that there was appreciation with respect to the carriage (the fuel takes up considerably less space product of ^H odnociujje also with regard to its calorific ^ VNE properties or the heating value of fuel after processing makes 31820 J / g (which is more than twice the original value).

The monthly balance can be determined as follows:

The tablets initially consisted of 256 g dry coal and 298 g water. At the end of the treatment, 207.3 g of the final product remained, containing 17.75 liters of gas (mainly carbon dioxide), corresponding to a consumption of about 35 g = 13.5% dry coal from the starting product and about 5.5% dry The carbon, based on the starting product, was converted to dehiet. The end product therefore contains 19% less dry carbon weight than the starting product.

From this mono-balance it is possible to calculate the following bullhead.

Starting product 555, 8 g mm yield 555, 8 x 1 2887 J = 7 136.8 kJ.

The final product in an amount of 500.3 g has a calorific value of 500.3 x 53 820 J = 6596.2 kJ.

The final product thus still measured 92.4% by weight of the thicker product, concentrated to 37% of the original volume and 37.4% of the original weight. The evaluation with jisSoSsu can therefore say that it has occurred.

The water content of the tablets to be processed was approximately 1% by weight.

In order to get an idea of the strength of the tablets in different degrees, the load at which the tablets begin to tear under pressure is determined

- the raw strength of the unprocessed tablets is 4,0 N,

- the tablets after processing at 250 ° C are 7,5 N, and

- the tablet strength after processing at 360 ° C is 29.8 N.

This clearly demonstrates that the strength of the tablets increases as a result of the recovery treatment, which may have great advantage in later processing. It is noted that the initial strength of pieces of the same brown coal (untreated) is 4.2 N.

The tablets are subjected to a crumb test (ASTM D 440 standard) to obtain the dust properties of the treated brown charcoal. Then, the test component is crushed in an appropriate manner, and after testing, the percentage of the small particle fraction in the remainder is determined by analysis.

- tablets heated to 250 ° C only: 33.0% of the moisture content disintegrated into particles smaller than 2 mm;

- Tablets additionally heated to 360 ° C: only 6,3% mono has broken up into particles of less than 2 mm, and

- lump coal of comparable diameter, which has been thermally dried at 84.0% by mass, has decomposed into particles smaller than 2 mm.

This clearly shows that the appreciation also occurred with respect to dust properties and manipulsvaaeenist ..

Example 2

Morwell brown coal (Australian brown coal with a water content of 61.2% by weight and a heat value of 10,886 J / g) is compressed at a pressure of 500 kPa to form uniform tablets (the same dimensions as in Example 1). The tablets are then heated to 340 ° C at 15.6 MPa for 1 minute (water vapor pressure at 340 ° C is approximately 14.9 MPa) in the presence of some inherent moisture.

During this treatment, the tablets shrink by 40%, the loss on processing being approximately 12% dry coal.

The final product has a water content of 34.6% by weight and a heat value of 20,767 J / g.

Here again it can be said that there has been an appreciation because the volume has decreased by 40% and the heat value is more than double ·

For the sake of completeness, it is noted that the water content of the brown coal is still considerable and that there is a possibility of further improvement.

In the crumb test, 1.9% of the recovered tablets are crushed to a fraction of less than 1.18 mm, while the recovered lump coal (particle size 7.5 to 12 µm) is crushed to a fraction of less than 1.18 mm. % By weight.

This shows that solid tablets with reduced water content are also produced in short-term recovery processing.

Claims (6)

SUBJECT OF THE INVENTION 1. A process for evaluating a less valuable fuel, which is in the form of fine particles of less than 25 mm, in which the fuel is heated to a temperature of 150 DEG to 375 DEG C. in the presence of water initially present in the fuel particles at a pressure greater than pressure. water vapor at the temperature used, characterized in that the fine particles are first formed into cohesive particles (before being subjected to a heat treatment) and then the cohesive particles are heat treated. 2. A process according to claim 1, wherein the cohesive particles are obtained by extrusion, briquetting, compression or upsetting. 3. The process according to claim 1, wherein the particles are formed at a pressure of 10 to 2500 kPa and preferably at a pressure of 100 to 1500 kPa. Method according to one of Claims 1 to 3, characterized in that particles having the largest dimension between 10 and 150 mm are formed. Method according to one of Claims 1 to 4, characterized in that a binder is added to the fine particles before they are formed into cohesive particles. Method according to one of Claims 1 to 5, characterized in that no fine particles of less than 5 mm and preferably less than 10 mm are present during the heating of the particles.