HU186751B - Method for improving the quality of low-class solid fuels - Google Patents

Abstract

A process for the upgrading of low-grade solid fuel by heating at a temperature above 300 DEG C in the presence of water, in which before or during the heating above 300 DEG C acid is added to the fuel.

Description

BACKGROUND OF THE INVENTION The present invention relates to a process for improving the quality of low quality fuels by heating at a temperature above 300 ° C in the presence of water: The object of the invention is to add acid to the fuel before or during heating. The process not only improves the quality of the main feedstock but also increases the tar yield.

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BACKGROUND OF THE INVENTION The present invention relates to a novel process for improving the quality of poor quality solid fuels by heating at temperatures above 300 ° C in the presence of water. As used throughout this specification and the claims, low grade solid fuel is understood to mean carbonaceous materials derived from photosynthesis of carbon and which may be at various stages of carbonization (such as biomass, plant material, waste, manure, peat and brown coal). The term low grade solid fuel also includes those materials described above which have already been pre-treated. For the sake of simplicity, all of these materials will be referred to herein as "fuel".

Such fuels usually contain a lot of water. The water is partly physically absorbed, partly bound in a gel structure, and partly in a chemically bound form. In addition, fuels contain many oxygen-containing groups. The calorific value of the fuels can be significantly increased by removing as much water as possible by dehydration processes and separating a significant portion of the oxygen-containing groups by decarboxylation techniques.

This removal is very easily accomplished by heating the material in the presence of water at temperatures above 300 ° C. Such a process is described in U.S. Patent No. 3,660,054, which discloses a heat treatment at a temperature of 315-375 ° C. Thus, a significant amount of water in the fuel is removed and extensive decarboxylation occurs. The calorific value of the resulting fuel increases significantly and its water content decreases. This gives us a much more valuable product than the starting material. Heating may also be carried out in the presence of water and / or water vapor, but the presence of water is essential for decarboxylation.

Heat treatment can also be combined with pre-treatment. For example, a heat treatment process involving such pretreatment is described in U.S. Patent No. 1,471,979. United Kingdom Patent Nos.

The fuel may contain tar prior to treatment, which may be removed by extraction. Heating at temperatures above 300 ° C may, in some cases, increase the amount of tar separated from poor quality solid fuels.

It has been found that the amount of tar produced during heating can be substantially increased by lowering the pH of the water present in the fuel.

According to the invention, acid is added to the fuel to be processed before or during heating above 300 ° C in the presence of water.

In addition to high-quality fuel, this process also yields significant amounts of tar. Thus, more than 10% by weight of poor quality fuel can be converted to tar. Preferably, at least a portion of the tar formed is isolated from the improved grade fuel and / or used for briquetting the improved grade fuel.

The resulting tar is typically highly aliphatic and contains only a few polyaromatic components.

The nature of the acid used in the treatment is immaterial. It may be an inorganic acid such as hydrochloric acid or sulfuric acid or an organic acid such as lignin sulfonic acid. Most preferably, formic acid and acetic acid may be used. Aromatic alcohols such as phenol may also be used.

The desired result is achieved by heating at temperatures above 300 ° C. The exact temperature depends on the fuel to be processed and is well above 300 ° C.

Heating can also be performed at pressures below 8.3 - 10 * Pa. The water released from the fuel then evaporates.

Continued heating at temperatures below the critical temperature of water (374 ° C) can prevent evaporation of water by working at a pressure greater than the vapor pressure of the water at the selected temperature. Thus, the water released from the fuel remains in a liquid state and in this form can be separated from the improved quality fuel.

During heating, part of the tar formed can be transported by steam or water and recovered from the transport medium. The tar present in the improved grade fuel can be recovered by various methods, such as solvent extraction, such as toluene, supercritical extraction, or azeotropic distillation, steam.

Preferably, the acid is added to the fuel so that the pH of the water present is 6 or less.

A further decrease in pH to between $ 3 and $ 5 can, in many cases, lead to a further increase in tar yield.

It may be advantageous to impregnate the fuel with the acid prior to heating so that the acid lowers the pH of the water present in the fuel. As a result, reactions leading to higher tar contents may occur earlier. Heating the fuel without excess acid can significantly reduce acid demand and reduce the risk of corrosion of the equipment used.

Preferably, after the addition of the acid, heating does not begin immediately so that diffusion of the acid into the fuel, especially if the latter consists of quite large chunks, is completed while the reaction between the fuel and the acid proceeds. This further reduces the amount of acid required.

Heating is carried out at a temperature above 300 uC under a pressure of 83 10 ° Pa (which means that no water is present during heating), the acid must be added to the fuel before heating. In this case, the fuel is preferably pretreated to remove most of the water prior to heating and then added before or during the fuel pretreatment. The pretreatment is carried out at a temperature of 150-300 ° C, at a given pressure above the water vapor pressure, and the pre-treated fuel is separated from the liberated water before being heated to a temperature above 300 ° C.

The great advantage of such a process is that much of the water present in the fuel is removed prior to heating to 300 ° C, at relatively low pressure without evaporating the water, and during heating above 300 ° C, very high decarboxylation, quality improvement & tar formation occurs at significantly higher temperatures without the need to increase the pressure. Evaporation of the small amount of water still present at heating above 300 ° C does not present any real disadvantage.

Thus, as described above, the heat treatment is carried out by:

186 751

(a) suspend the fuel in water, pre-treat the water with a pressure higher than the vapor pressure at the temperature applied, separate the fuel from the water and heat it at 300 to 374 ^{U at} 9,8 to 10 ⁴ -10 ⁷ Pa; adjusting the pH of the water to pH <6.0 before or during the fuel pretreatment or before or during heating, or

b) the fuel is suspended in water at a temperature of 300-374 ° C for 9.8 to 10 -2 ⁴ · 10 ⁷ Pa is heated and the pH of the water in the heating material is adjusted with acid to pH <6.0, before or during the heating.

Further details of the invention are illustrated by the following examples, without limiting the invention to the examples.

Example 1

10 parts by weight of Australian brown coal containing 60.0% by weight of water and 1.0% by weight of ash are suspended in 6 parts by weight of water. Technical suspension of glacial acetic acid is added until pH is reached (14 parts of glacial acetic acid per 1000 parts by weight of brown carbon) and the mixture is heated in an autoclave at a heating rate of 8 ° C / min to above 340 ° C.

The autoclave is then opened and the water (pH 4.0) is separated and separated by a carbon filter. This gives 15% by weight of water-containing hard black carbon.

The resulting hard black carbon is then extracted with toluene. During the extraction, 6.8% by weight of tar, based on the amount of starting brown carbon, is dissolved.

for comparison, the original brown coal is extracted with toluene. Thus, a tar equivalent to 1.2% by weight of brown carbon is dissolved.

For further comparison, the above improvement in brown coal quality is repeated, with the exception of glacial acetic acid. Thus, the resulting tar yield is 2.4% by weight based on the amount of original lignite and the pH of the water after the quality improvement is 7.5.

The above example, together with the comparative experiments, demonstrates that there are conditions under which the acid treatment of a brown coal prior to heat treatment above 300 ° C affects the tar yield.

Example 2

Cow manure is suspended in water and glacial acetic acid is added to a pH of 4.5. The suspension is heated in an autoclave to 325 ° C and the carbon is filtered off. In this quality improvement process, based on 100 parts by weight of ash and anhydrous material present in the cow manure, 40 parts by weight of ashless and anhydrous carbon are obtained from which 25 parts by weight of tar can be extracted by extraction.

If this experiment is repeated without glacial acetic acid (in this case, the pH of the aqueous slurry of cow manure is 24), 24 parts by weight of ash-free and anhydrous charcoal per 100 parts by weight of ash-free and anhydrous material can be obtained.

With the extraction feed of the cow manure itself, only 4 parts by weight of tar per 100 parts by weight of ash-free and anhydrous starting material can be obtained.

This example shows that the process of the invention increases the amount of tar that can be extracted from cow manure.

Example 3

2500 g of the Austrian brown coal used in Example 1, containing 1500 g of water, 975 g of organic material and 25 g of ash, are pretreated in aqueous suspension to pH 33 at 240 ° C. This pre-treatment is carried out in an autoclave at a pressure higher than the vapor pressure of the water vapor at 240 ° C. After removal of the aqueous liquid phase, 1300 g of partially carbonized product are obtained, containing 300 g of water, 975 g of organic material and 25 g of ash.

This product was further treated at atmospheric pressure at 340 ° C with direct heating with superheated water vapor. 645 g of anhydrous carbon are obtained, containing 25 g of ash and 140 g of tar. The tar is transported by steam and recovered by condensation. In this case, tar is obtained in a yield of 5.6%, calculated on the basis of brown coal.

Example 4

1000 g of used in Example 1 of Australian brown coal, comprising 600 g water, 390 g organic material and 10 g ash from an aqueous slurry, after adjustment to pH 3.0 with ^u pretreated by heating to 250 ° C. The heating rate is 10 ° C / min. The pretreatment is carried out in an autoclave at a pressure above the water vapor pressure of 250 ^uC for 30 minutes. Separation of the aqueous liquid phase gave 520 g of a partially carbonated product containing 120 g of water, 390 g of organic material and 10 g of ash.

This product is further heated at 50 bar to 340 ° C. The heating is carried out directly with superheated water vapor at a heating rate of 8 ° C / min and the heating is turned on immediately when reaching 340 ° C. This gives 258 g of anhydrous carbon containing 10 g of ash and 56 g of tar.

Without isolating the tar, the product is pressed into briquettes having a diameter of 113 mm. The resulting briquettes have a compression strength of 299 Newton.

for comparison, the two-step procedure is repeated under the same conditions with the only difference that the pH in this case is kept at 8. The briquettes thus produced have a compression strength of only 6.1 Newton.

Australian brown coal briquetting itself (no heat treatment at all) yields briquettes having a compressive strength of only 4.0 Newton. The product obtained in the first step of the two-stage heat treatment is pressed to obtain briquettes having a compression strength of 6.0 Newton at pH 8 and 73 Newton at pH 3.

PATENT CLAIMS

Claims (2)

A process for improving the quality of low grade solid fuels by optionally pre-treating the fuel at 150-300 ° C and then heating it at a temperature above 300 ^{U in} the presence of water, 186 751 a) the fuel is suspended in water, pre-treated with a higher water showed the temperature employed, the vapor pressure of pressure, and the fuel is separated from the water and heated to 300-374 ° C, 93 · 10 "-2 · 10 ⁷ Pa, and the pH of water in the fuel material - adjusts its pH to 6j0 before or during fuel pretreatment or before or during heating, or b) the fuel is suspended in water at a temperature of 300 to -374 ° C J8 9 * 10 * ⁷ .10 heated -2 torr and the pH of the material in the heating water adjusted to pH <6.0, before or during the enlargement HE5. 2. The l. Method according to claim, characterized in that the acid is added and the heating was carried out at 83 to 10 · ^e Torr prior to heating.