Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound
Reexamination Certificate
1998-12-01
2001-02-27
Griffin, Steven P. (Department: 1754)
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
C423S062000, C423S064000, C423S138000, C075S420000, C075S425000, C075S430000, C075S622000, C075S628000, C075S629000
Reexamination Certificate
active
06193941
ABSTRACT:
The invention relates to a process by which, from a heavy-metal containing oil, in addition to synthesis gas, a metallurgical raw material is generated.
It is known that oils can be contaminated with heavy metals. This applies in principle to all petroleums, whose quality, in addition, is becoming increasingly poorer as resources decrease, particularly to those from Venezuela and Russia, but also to refinery residues, bitumen, waste oils and pyrolysis oils. The heavy metals vanadium and nickel occur particularly frequently as contaminants. In the energetic or material conversion of such oils, the heavy metal content leads to problems: firstly, during combustion or a partial oxidation, heavy metal compounds are formed which develop extremely corrosive actions and, at the prevailing working temperatures, can become molten or pasty, and as a result of which have a tendency to cake, subsequently leading to breakdowns. Secondly, these heavy metal compounds may be emitted only in very low amounts in the gaseous or liquid state. Land filling in solid form is expensive and is subject to strict legal provisions. For these reasons, plant operators preferentially have recourse to oils having low heavy metal contents, which decreases the value of heavy-metal-containing oils.
The present invention solves the problems described by the features of claim
1
covering a process for generating metallurgical raw material from heavy metal containing oil comprising:
(a) separating off and burning the heavy metal containing soot, wherein the heavy metals is produced as ash;
(b) scrubbing out from the resulting synthesis gas by means of an aqueous scrubbing solution the soot formed in the partial oxidation which comprises the heavy metals in adsorbed chemical compounds;
(c) filtering the scrubbing solution in a chamber filter press in such a manner that the filtrate obtained initially is collected and filtered again;
(d) producing the filtercake which comprises virtually all the heavy metals and dried it to a residual moisture of less than 10% in a spray dryer, a pneumatic dryer or a mill drier by heated inert gas;
(e) burning the dust-formed soot thus conditioned in a pulverized fuel burner allowing for a maximum grain size of dust particles size of ≦140 &mgr;m at a temperature of 900 to 1000° C. and at an oxygen content above 1%, maintaining a reaction time of at most three seconds, preferably 1 second;
(f) cooling the flue gas formed to 450° C. to 650° C. immediately following the combustion by addition of an or inert gas or water or deducted cooled flue gas; and
(g) releasing the heat in the combustion and using it for heating up the inert gas used in the drying process.
The heavy-metal-containing oil is converted in a plant for partial oxidation, termed oil gasification below. Customarily, in a plant for gasifying liquid or solid carbonaceous fuels, only an incomplete conversion of the carbon compounds takes place. This is due to the fact that an oxygen deficit prevails within the flame in which the reaction principally takes place. This oxygen deficit results from two causes: firstly, the partial oxidation requires considerably less oxygen than combustion, therefore oxygen is added relatively sparsely. Secondly, an approximately perfect mixing of oxygen with oil mist is technically very difficult to achieve, so that within the reaction zone, areas having a relatively large oxygen deficit coexist together with areas well supplied with oxygen. The poorer the mixing, the more soot is formed. In a development of the present invention, the three- or multistream burner achieves the object of ensuring particularly good mixing and distribution of fuel and oxidizing agent.
A customary technique of disposing of soot is to recycle it to the gasification reactor. In this recirculation, a majority of the recirculated soot is converted into synthesis gas. Direct recirculation of heavy-metal-containing soot from an oil gasifier into the gasification reactor would lead to an enrichment of the heavy metals in the gasification reactor and in the subsequent apparatuses, and as a result would lead to the operating problems mentioned above. Therefore, the heavy metals must be separated off from the soot in a complex manner before recirculation of the soot to the gasification reactor is technically expedient. This is customarily achieved in an extraction unit in which naphtha serves as extraction medium. Since such a separation never succeeds perfectly at acceptable cost, heavy metal enrichment in the gasification reactor and downstream devices must always be expected.
In another process, described in laid-open application DE-43 09 825, the filter cake is treated with acid. The acid here dissolves the heavy metals from the soot.
A further feature of the present invention is that the soot formed in partial oxidation which comprises the heavy metals in adsorbed chemical compounds is scrubbed out of the resulting synthesis gas by means of an aqueous scrubbing solution.
From GB-A-1 178 267 the technology of the a of soot is known, wherein the soot-water suspension of a further treatment is undertaken.
The present invention therefore avoids the complex separation of the heavy metals from the soot, which is advantageously accompanied by considerable savings in the equipment requirements and an increase in the operational reliability. It is desired here to obtain soot having as high a content of heavy metals as possible, since the heavy metals support the combustion process and are separated off on a filter after the soot combustion. Only apparatuses with which no operational problems are expected are provided. A separation process for soot and heavy metals can therefore be omitted; the separate combustion replaces the separation process.
It initially appears a disadvantage that the energy present in the soot is not produced in the form of synthesis gas. If the soot were recycled to the gasifier, the carbon would be converted to synthesis gas. Surprisingly, the conversion of oil to synthesis gas in a three- or multistream burner succeeds so well that only very little soot is formed. This correspondingly has a high heavy metal content, which fits in with later metal recovery by combustion and is another advantage. Because of the very high yield of a three- or multistream burner, the loss in synthesis gas yield is extremely low in comparison with the customary technology using complete soot recirculation, so that soot recirculation even from the energetic point of view would no longer be worthwhile.
Therefore, special developments of the present invention have been created in which heavy-metal-containing oil is fed to a partial oxidation stage, which is preferably equipped with a three- or multistream burner, which achieves a high conversion of carbon to synthesis gas and generates correspondingly little soot.
In contrast, it is possible to remove more usable heat from the synthesis gas, since accumulation of heavy metals due to soot recirculation no longer occurs, and as a result it becomes possible to use heat exchangers for the waste-heat utilization at a higher temperature without the risk of exposing them to the risk of clumping and corrosive attack. The overall efficiency of a combined cycle gas turbine power station with integrated gasification for producing electrical energy from synthesis gas can thus be improved, for example, by up to 5 percentage points, which is a further advantage of the invention.
The soot, which essentially comprises the unreacted carbon, is discharged in dust form from the gasification reactor and comprises heavy metal compounds in solid form. In a subsequent water scrubbing, which can be connected downstream of the waste-heat utilization, the soot is separated from the process gas. It is present thereafter as a 1% strength aqueous suspension, termed “soot water” below. The heavy metal compounds are present in the soot water both in dissolved form and in solid form bound to the soot particles.
After a pressure reduction of the soot water and, if appropriate, steam stripping, the heavy-me
Buxel Michael
Keller Heinz Jochen
Griffin Steven P.
Ildebrando Christina
Krupp Uhde GmbH
Rosenman & Colin LLP
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