AU598314B2 - Method and device for mineralization of carbonaceous materials - Google Patents

Description

59831COMMONWEALTH OF AUSTRALIA COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 Form SUBSTITUTE COMPLETE SPECIFICATION FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: t z I t 5, 555 C S c t t st l I Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Related Art: This document contains the amendments made under Section 49 and is correct for printing.__ This, document contains the amendments allowed un'-r Section 83 by the Supvising Examiner on and is correct for printing TO BE COMPLETED BY APPLICANT I 51 *t 45 t ex t* i: t t te 5 T; t5t 5, :5 44 V 44 t i Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: TESSEK sdruzeni Praha 3 Krizovnicka, 110 00 Praha 1,

CZECHOSLOVAKIA

Petr Puschel; Zdenek Formanek; Vaclav Krivanek; Antonin Pokorny; Anna Vlasakova and Alena Stuchlikova GRIFFITH HASSEL FRAZER 71 YORK STREET SYDNEY NSW 2000

AUSTRALIA

Complete Specification for the invention entitled: METHOD AND DEVICE FOR MINERALIZATION OF CARBONACEOUS MATERIALS The following statement is a full description of this invention, including the best method of performing it known to me/us:- 3020A:rk GRI;FFITH, HASSEL FRAZ E Box 2133 G.PO., SYDNEY 2001. AUSTRALIA.

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The invention relates to a method of mineralization of carbonaceous materials e.g. f'r following dissolution and chemical analysis for determination of the content of chemical elements, incl. trace elements in foods, fodder, in plant and animal tissues and other materials.

The decomposition of carbonaceous materials for chemical analysis presents itself as a method of treatment of an either solid or liquid specimen in either genuine or pre-treated state, e.g. by grinding, drying or homogenization. The decomposition consists of two phases: the mineralization, i.e. oxidation of carbonaceous compounds present, and in dissolution of the mineral residue, the two phases being carried out, if desired, simultaneously. The product of the decomposition is a homogeneous solution.

This solution can be chemically analyzed by one of either chemical or physico-chemical methods. The limiting factor ,n determination of elements, particularly of trace elements, is their concentration in blank tests. The latter Ce include all increments and decrements of the sought crt0o elements, occuring during the treatment of the specimen of S the tested matter, till to the end solution. Thus, it includes also the manipulation with the specimen, use of tools, aids and chemical glassware, influence of the purity Sand amount of the chemicals used, as well as further 25 objective and subjective influences of the workers preparing the specimen. The background established by blank tests is then used for the correction of the results of the analysis. In the analytic chemistry there are advantageous such methods of the decomposition that use a small number of decomposition steps and small amounts of chemicals. Thereby r the ratio of the concentration of the sought substance in the specimen and in the blank test is favorably influenced.

In this way it is possible to attain a more suitable limit Sof. the estimation accuracy and reproducibility of the results. The whole analytic system, i.e. the process from Staking the specimen of the respective material till to the results of the analysis possesses then high stoutness and accuracy, what is the main condition of success in the analytic chemistry.

6097S/ls -lA- 'i The known methods of mineralization of carbonaceous materials, e.g. of all sorts of foods, forages, animal and plant tissues are using either wet or dry techniques of decomposition, or a combination thereof.

Wet decomposition of the specimen is e.g. the mineralization according to Kjeldahl, described in "Zeitschrift fur Analytische Chemie", page 366/1883/, where the specimen is combusted in the medium of a great surplus of concentrated sulfuric acid, said acid being, in presence of a catalyst, simultaneously the oxidation agent. Kahan's method, published in "Zeitschrift fur Analytische Chemie", 107, page 11/1937/ uses, at similar conditions, a mixture of nitric, perchloric and sulfuric acids. The disadvantage of this method is high acid concentration and the presence of i 1A1 the catalyst in the resulting solution, further the S necessity of separation of the eventual insoluble remainder ~and its dissolution by another method.

Wet methods of mineralization are often modified by 00 0 methods recommended by producers of analytical apparatusses, .0o e.g. see the material of the company Varian Techtron, "Food analysis by atomic absorption" /1073/. Such methods consist in defined action of various combinations of acids and further chemical agents onto the analyzed specimen. Thereby a leach of the specimen is obtained rather than a true solution. The sought substance is but partly, undefinably O6c dissolved and its remainder is bound onto the solid particles contained in the leach with various strength.

*0 This fact decreases considerably the exactness of the chemical analysis.

O The decomposition in a Paar's bomb, described e.g. by Pischel in "Zpravodaj VUHU/Report of the Research Institute of Brown Coal", Most, page 3/1972/, and in the materials of the company Hans Krner, Neuberg/1984/, consists in combustion of the specimen in oxygen under pressure, flushing the bomb, separation the undissolved particles and their dissolution in acids. The shortcoming of this method is bad solubility of the remainder, melted together at high 6097S/ls temperatures of the calcination, extensive manipulation with the specimen and contamination from the metallic, though teflonized bomb internal surface. All this leads to high and fluctuating concentrations of the sought substance in blank tests, whereby the accuracy of the analysis is limited: The burning of the specimen in the air at the temperatures ranging from 500 to 850°C, if desired in presence of sulfuric acid, as described by Feinberg and Ducauze, "Analytical Chemistry" 52, page 207/1980/, causes losses of volatile elements such as Cd, Pb and As, burning in an air stream with nitric acid vapors at 550°C, published by Gag in "The Analyst" 80, page 789/1955/, was verified but for lead, moreover there were observed remnants of the incompletely combusted organic matrix.

Another method of mineralization of the specimens for Schemical analysis is combustion in a low-pressure plasma discharge, published by Gleit, and Holland, in the "Analytical Chemistry" 34, 1454/1962. The combustion is Scarried out under pressure of several hundred Pa at temperatures below 200 0 C. The low temperature decreases the losses of the sought substance by volatilization, on the c* other hand, however, the use of a low pressure diminishes this effect considerably. Furter shortcoming is the necessity of a rather complicated and expensive apparatus and troublesome manipulation with the specimen.

00 Further used methods of mineralization were published by Cibulka et al in the book "Pohyb olova, Kadimia a rtuti v zemedelske vyrobe a biosfere" /The Travel of Lead, Cadmium and Mercury in agriculture production and biosphere/, edited by SZN /State Agriculture Editory/ in Prague /1986/. It uses a sequence of operations: k r Carbonization of the dry substance of the specimen at S400 0 C, long-time combustion at 500°C, subsequent mineralization by concentrated nitric acid and calcination at 500-550 0 C. The use of comparatively high temperature is again disadvantageous, as well as the exacting manipulation of the specimen, so that a contamination and partial loss of the substance are possible.

6097S/ls -3- The equipments for dry mineralization used up to date can be divided in three groups: The first group consists in equipments working in an open system. Such equipments make possible drying of the mineralized material and following carbonization and final combustion in presence of air, or, if desired, in an atmosphere with an increased oxygen content at atmospheric pressure and at a final temperature of 450 to 850°C. The combustion flasks can be made e.g. from a ceramic material, from quartz or silicate glass. The combustion medium is usually formed by an electrically heated oven with regulation. For the drying and the carbonation phases one can use also electric or gas heaters, heated plates or heated blocks, surrounding partly the flasks. All these equipments have the common shortcoming of being "too much Sopen". The result is an increased possibility of contamination, undesired particularly in trace- and ultra-trace analysis.

9 The comparatively high temperature can, on the other 0O hand, cause a loss of some of the sought elements, or an agglomeration can at such high temperatures occur, or even melting of the ashes which can be then dissolved but with high difficulties.

Second group consists in equipments working at increased oxygen pressure in a closed system. This group is 64 represented by an equipment consisting of a Paar's bomb with teflonized inner walls. The specimens are weight into 0: special microthene R bags and in the bomb, ignited by a metallic or graphite igniting, fibersi After the combustion of the specimen the mineralized matter is quantitatively flushed out from the bomb and the solid part is separated and decomposed by acids. The solid part of the mineralized matter is usually formed by a melt which cannot be easily decomposed. Further shortcoming is the possibility of contamination by the metal of the bomb and the high number of manupulations with specimen. Still another disadvantage resides in high time requirements of the cycle caused mainly by the filtration of the mineralized matter.

6097S/1S -4i i The last group includes mineralization equipments working with an oxygen stream in a plasma discharge at the pressure of several hundred of kilopascals at temperatures 150 to 200 0 C. The equipment, both electric and pressure parts are complicated.

The disadvantages mentioned at individual methods of mineralization of carbonaceous materials are avoided by the present method, wherein the specimen is heated to a temperature 300-400°C for 6-20 hours at atmospheric pressure in a stream of oxygen at the rate of 0.03 to -1 -1 0.15ml.s .g of the specimen, adding a gas with a higher oxidation strength than that of the oxygen, said gas being selected from the group consisting of ozone, nitrogen oxides, chlorine and their mixtures, such as ozone/nitrogen I 15 oxides, chloroxides of nitrogen, in an amount of 1 to 6 volume percent.

",The mineralization of carbonaceous materials according to the present invention takes place at temperatures by 200 S4 to 500°C lower than in the dry mineralization methods used up to now, so that the possibility of volatilization of the i"s* analyzed elments is limited to a minimum. By the reaction ai of single components of the gaseous mixture there are formed unstable compounds such as nitrosyl-, peroxide or nitrosyl chloride, with a higher oxidative effect than the sum of the 25 effects of individual components. Due to the high oxidative strength of the gas mixture the specimen is perfectly combusted and the remainder does not need any subsequent oO:. oxidation. At the low temperature used and the controlled oxygen inlet the specimen does not light up under local overheating that would cause losses of the estimated S substance, sintering of the ashes and decrease of their reactivity and solubility. The choice of the mixture of oxidative gases is given by the purpose for which the specimen is decomposed. So e.g. if elements forming 35 volatile chlorides, such as Ge, As, Sn, Sb, Pb and similar are the be determined chlorine will not be used.

I' ST R 41 0FVi 6097S/ls The structure of the ashes corresponds to that of the originally bound substances, the ashes are in activated physical form and are easily decomposed by a small amount of mineral acids. The resulting solution has therefore a low and exactly defined acid concentration. The number of operations leading to the solution is small, resulting in small and constant values of blank tests. The needed amounts of pure chemicals for the decomposition is minimal.

The method is universal, many sorts of various materials can be worked with only small modification of conditions. If a multiple equipment is used, it is possible to prepare a large number of specimens simultaneously.

The shortcomings mentioned at individual equipments for dry mineralization are avoided by the equipment for the mineralization of carbonaceous materials in dry phase by means of a gas phase according to the present invention.

The substance of the invention consists in the use of :mineralization unit that is formed by a heatable block, advantageously from an aluminium alloy, which block is provided with cylindrical holes with flat bottom for inserting the mineralization flasks with the specimens.

0 CR Each block is covered by a lid, advantageously also made from an aluminium alloy, which lid is provided by openings for the necks of the mineralization flasks. Mineralization S* .25 flasks have cylindrical shape tapering conically towards the 0 cylindrical neck. Inlet capillary tubes are loosely inserted therein, said capillary tubes being in their top parts annexed to the distributor of the mineralization gas mixture. The bottom end of the inlet capillary tube can advantageously transit into the tubular part.

.p The distributor of the mineralization gas mixture can be connected through a cooler, condensate separator and mixing tube with the ammoniac furnace, provided with inlets for oxygen and ammoniac, and with ozonizator with oxygen inlet, where the mixture of mineralizing gases is prepared.

SIf chlorine is used as a component of the mineralizing gas mixture, the distributor of the gas mixture is provided with an inlet for chlorine.

6097S/ls -6- The distributor of the mineralizing gas mixture can be directly connected, however, with containers or sources of single gases as needed.

The block of the mineralization unit as well as the ammonia burning furnace and the ozonizator can be connected with a source of electric energy.

The mixing tube, the condensate separator, the cooler, the distributor of the gas mixture, chlorine inlet, mineralization furnace, inlet capillary tubes and their connecting elements are made from a material resistant to oxidation.

The device for the mineralization of carbonaceous materials according to the invention makes possible to act onto the specimen in solid phase by a gas phase at determined conditions. The solid phase of the specimen can be obtained, if desired, in the mineralization equipment of the invention by drying, degasification and evaporation of semi-solid or liquid specimens. The reacting gas phase !11;2 makes possible a controlled burning, where the oxidizing matter are components of the gas phase such as oxygen, ozone and nitrogen oxides. The advantage of the device for the o. mineralization of carbonaceous materials according to the invention is the controlled combustion shifting the reaction equilibrium towards obtaining mineralization products by a.25 constant addition of fresh gas mixture while simultaneously leading off the gaseous mineralization products. Thereby a perfect mineralization product can be obtained, the *o microstructure and texture are but slightly impaired in comparison with those of the original specimen and are very favorable for the following dissolution of the ashes. The device for the mineralization of carbonaceous materials according to the present invention makes possible to control, according to a heating schedule, the drying, degassing and, in the last phase, the mineralization in such a way that the whole mineralization flask is evenly heated and any forming of unburnt sediments in the neck of the flask and any overheating of the mineralized material are avoided.

A 6097S/ls -7- The losses of the determined elements are practically excluded due to the low mineralization temperature. The half-closed mineralization device decreases to a minimum the possibility of contamination of the specimen by impurities from the environment.

The annexed drawing shows an example of the device for mineralization of carbonaceous materials according to the invention wherein on the Fig. 1 it is diagrammatically illustrated in a general view and on the Fig. 2 is the mineralization unit.

The device for mineralization of carbonaceous materials consists of the ammoniac combustion furnace 1 provided with an oxygen inlet 2 and ammoniac inlet 3, and of the ozonizator 4, provided with the oxygen inlet 5. The ammoniac combusting furnace 1 and the ozonizator 4 are connected by the mixing tube 6 with the condensate separator S0,. 7, provided with the outlet 8, into which there are led the reaction products of the ammoniac combusting furnace 1, i.e.

a mixture of oxygen, water vapors, nitrogen oxides and 20 reaction products from the ozonizator 4, i.e. an oxygen-ozone mixture. The condensate separator 7 is connected with the cooler 9, which is connected by the distributor 10 of the gas mixture with the mineralization unit 12. If chloLine is added to the mixture of mineralization gases, the distributor 10, of the gas mixture 9 tc is provided with an inlet 11 of chlorine.

The mineralization unit 12 consists of the block 13 of I e.g. cylindrical or prismatic shape, made from an aluminium "alloy, electrically heated and provided with cylindrical holes with flat bottom for inserting the mineralization flasks 15. The specimens are inserted into said mineralization flasks. The block 13 is above covered by a lid 14, also from an aluminium alloy, provided with openings for the necks of the mineralization flasks 15. The flasks 15 are cylindrically shaped, tapering conically towards the cylindrical neck. Into the mineralization flasks 15 there are loosely inserted inlet capillary tubes 16, that are in 6097S/ls their top part connected with the distributor 10 of the gas mixture. The lower end of the capillary 16 transits into the tubular part.

To avoid undesired corrosion by the streaming mineralization gases the mixing tube 6, separator 7 of the condensate, cooler 9, distributor 10 of the gas mixture, inlet 11 for chlorine, mineralization flasks 15 and inlet capillary tubes 16 as well as their connection elements are made from a corrosion-resistant material, e.g. from quartz, glass or polytetrafluoroethylene.

The device for mineralization of carbonaceous materials consists furthermore of the source 17 of electric energy, which is connected with the ammoniac burning furnace 1 and the ozonizator 4 for the preparation of the mineralization gas mixture and with the block 13 for scheduled heating.

Mineralization gas mixture for the mineralization of carbonaceous materials is in this case prepared in following a way: 0 In the combustion furnace 1 is a mixture of ammoniac and oxygen burnt on a catalyst under formation of nitrogen **to oxides, another stream of oxygen is enriched by ozone in the ozonizator 4. The gases are then led together into the condensate separator 7, where the reaction water and nitric acid are separated, By the reaction of nitrogen oxides,, oO.25 superfluous oxygen and ozone, higher nitrogen oxides and peroxo-compounds are formed. After full separation of water S from the gas mixture and, if desired, addition of chlorine to the mineralization gas mixture the gas stream is led by the distributor 10 of the gas mixture into the inlet capillary tubes 16 to the specimens to be mineralized. The specimens are placed in mineralization flasks 15 that are in their whole volume uniformly heated, according to the program, in the mineralization block 13.

The mineralization itself is carried out so that the weighed specimens are heated according to the optimalized program, regarding the character of the mineralized material. An effective action of the mineralization gas 6097S/ls -9i~Lii~iiu\_iiil_ IA At f mixture is made possible by its leading into the space of the specimen, where a constant exchange of the meta-stabile, strongly oxidative reacted compounds by fresh ones takes place. The reaction products are entrained by the stream of the non-reacted gas over the lid 14, of the mineralization unit 12, whereby a shift of the reaction equilibrium towards the mineralization is reached, the stream of escaping gases preventing the penetration of undesired impurities into the mineralization flask In the following lines there are given several examples of the invention.

Example 1.

A specimen of dry animal muscle, weight 2 g, was heated for 20 hours to 400 0 C, in a stream of oxygen 0.06ml.s 1 the oxygen containing 5% of nitrogen oxides.

S Example 2.

A specimen of grain flour weighing 2 g was heated for 18 hours to 400°C in a stream of oxygen containing 5% of S nitrogen oxides and 1% ozone. The gas mixture was streaming at the rate of 0.2 ml.s 1 Example 3.

Specimen of 0.6 g of cottom was heated for 6 hours to 300 0 C in a stream of oxygen 0.09 ml.s containing 5% of ozone.

Example 4, n A specimen of grain straw, weighing 1 g, was heated for S 12 hours to 3800C in a stream of oxygen containing 1% of S,0, nitrogen oxides and 5% of ozone, at a rate of 0.lml.s- Example Specimen of a mineral oil, weighing 2 g, was heated for 20 hours to 300 0 C in a stream of oxygen containing 1% of nitrogen oxides and 5% of chlorine, at the rate of -1 0.1ml.s Example 6.

A specimen of butter, weighing 1 g, was heated for hours to 350 0 C in a stream of oxygen containing 5% of nitrogen oxides and 1% of chlorine, at the rate of 0.65 Sm.s-1.

ml.s.

6097S/1S 0^ l In all Examples the product of the mineralization was a loose ash easily soluble in 15% nitric acid. The ash of the grain straw and that of the flour were wetted before the dissolution with hydrofluoric and perchloric acids, whereafter the acids were boiled off.

The method of mineralization of carbonaceous materials of the present invention can be also utilized for the establishing of the structure of the mineral skeleton of carbonaceous materials or also for careful obtaining ashes of carbonaceous material for technological working.

60 o a a 0 a 0 9 0 °6 o 06 S.4

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6097S/ls -11-

Claims (9)

1. A method of mineralization of carbonaceous material comprising: i) heating a specimen to a temperature ranging from 300 to 400°C for 6 to 20 hours at atmospheric pressure; in a stream of oxygen at a rate of 0.03 to 0.15 -i -I ml.s .g of the specimen, ii) adding to said oxygen, a gas possessing 'higher oxidative strength than that of oxygen, selected from the group consisting of ozone, nitrogen oxides, chlorine and o mixtures thereof like a mixture of ozone with nitrogen 600 S' a, oxides arid chloroxides of nitrogen, in an amount of 1 to 6 S ooo. volume percent. eo

2. A device when used for performing the method of claim 1, characterized by a mineralization unit, comprising a heatable block, which is provided with a plurality of cylindrical oo' holes for accommodating mineralization flasks containing the specimens, the mineralization flask body being of Sao* cylindrical shape, conically tapering towards a cylindrical neck wherein the block is covered by a lid provided with openings for the necks of mineralization flasks, the flasks containing loosely inserted capillaries connected at their top parts to a distributor of a mineralization gas mixture

3. A device according to claim 2, characterized by 4 30 that the distributor of the mineralization gas mixture is connected through a cooler, a condensate separator, and a mixing tube to an ammoniac combusting furnace which is ii provided with an oxygen inlet and an ammoniac inlet and to an ozonizator, provided with an oxygen inlet. -13-

4. A device according to claim 2 or 3, characterized by that the bottom end of the capillary transits into the cylinderical body of the flask.

5. A device according to claim 2, 3 or 4, wherein the block is connected to a source of electricity.

6. A device according to claim 5, characterized by that the source of electricity is connected to the ammoniac combustion furnace and to the ozonizator. r t C C C

7. A device according to any one of claims 2-6, characterized by that the mixing tube, condensate separator, cooler, distributor of the mineralization gas mixture, mineralization flasks and inlet capillaries, as well as their connecting elements, are made from an oxidation-resistant material.

8. A method of mineralization of carbonaceous material substantially as described with reference to any S one of the Examples.

9. A device when used for performing the method of claim 1, substantially as described with reference to the S 25 accompanying drawings. DATED this 27th day of March 1990 TESSEK SDRUZENI PRAHA By their Patent Attorneys GRIFFITH HACK CO. V i r