JPH06340883A - Preparation of synthetic gas - Google Patents

Abstract

PURPOSE: To environmentally safely treat by-produced carbon particles, metals and/or metal compounds by cooling crude synthetic gas obtained by partially oxidizing, particularly high-ash liquid, semisolid or solid hydrocarbons, cooling and scrubbing the crude synthesis gas with water and treating the filter residue of the washed water with an acid.

CONSTITUTION: Crude synthesis gas obtained by the partial oxidation of hydrocarbons is cooled in a radiant cooler and then in a convection cooler and subsequently scrubbed with water in a wet separator. This washed water is optionally combined with the aqueous phase of the radiant cooler and separated, in a separation apparatus (preferably, a filter press) into a residue essentially containing carbon, metals and/or metal compounds and water and purified water as the filtrate. The steam-saturated crude synthesis gas is cooled to separate off water and solid-free synthesis gas is obtained. Said filter residue is optionally partially dewatered in said separation apparatus and then treated with an acid to take off the resulting metal salt solution and the remaining carbon is returned to the partial oxidation step.

COPYRIGHT: (C)1994,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is particularly concerned with heavy metals which are produced together with carbon particles when various ash-rich raw materials such as heavy oil and bitumen are used in various forms, including emulsions made from bitumen. It relates to a process for the production of synthesis gas from liquid, semi-solid or solid hydrocarbons, in particular ash-rich hydrocarbons, in an environment-friendly separation.

[0002]

German Patent DE-A-4117266 describes a process for producing synthesis gas by partial oxidation of ash-rich hydrocarbons. In this case, the hydrocarbons are oxidized under conditions such that about 0.1 to about 0.3% by weight of the carbon used as the hydrocarbon forms carbon particles. The crude gas is cooled first in a radiant cooler, then in a convection cooler, and it is washed with water in a wet separator. Carbon particles are suspended in the generated washing water, and various solid and gaseous substances are dissolved and contained therein. This is optionally combined with the aqueous phase of the radiant cooler, filtered, and sent back to the gasifier. The steam-saturated crude gas is cooled in a heat exchange system, and the separated water is sent back to a water treatment unit except that which is also sent back to maintain the water level in the unit. Be guided. This mode of operation ensures that, depending on the process-based conditions, various heavy metals are not released from the gasifier along with its wastewater.

One of the essential characteristics of this process is that most of the carbon supplied in the form of hydrocarbons is converted into carbon monoxide, whereby only 0.1 to 0. It means that only 3% by weight appears as carbon particles. In this way the raw material is optimally utilized. At the same time, a solid phase is formed, which consists of carbon particles which act as a filter aid and a high concentration of metals or metal compounds. It contains almost all the metallic impurities of the heavy oil, and only a very small portion is deposited in the gasifier.

The proportion of carbon particles in the reaction product is adjusted in a known manner by the amount of oxygen supplied. This known method has proven to be excellent, since it satisfies both high economic requirements and high requirements for environmental pollution. Only the treatment of its solid phase consisting of carbon particles and heavy metal compounds is not yet completely satisfactory. The continuous feeding of carbon particles back to the gasifier for the purpose of reacting is not taken into account, as this results in the undesired deposition of metals and metal compounds in the apparatus. Treating a mixture of carbon particles, metals and / or metal compounds outside this apparatus is also problematic due to the large amounts produced. The finely divided solids retain water and form with it a mixture containing 80 to 90% by weight of water. Moreover, the metals are present as sulphides and further processing of them cannot be done anywhere, as this requires various special safety measures. The oxidative treatment leads to the formation of sulfur dioxide, as the wet chemistry by dissolution in various acids leads to the generation of hydrogen sulphide. Finally, it is not only a significant practical difficulty to pass on various substances to others that the treatment is not dangerous from an environmental point of view, but also management difficulties.

[0005]

Therefore, within the framework of the process for producing synthesis gas from various hydrocarbons, the environmentally friendly mixture of carbon particles, metals and / or metal compounds which is produced in the purification of synthesis gas is to be used. The problem exists of providing a method that allows an acceptable treatment.

[0006]

According to the present invention, this object is achieved by forming a crude synthesis gas containing 0.1 to 0.3% by weight of carbon particles with respect to the carbon used as a hydrocarbon. Partial oxidation of semi-solid or solid hydrocarbons, especially ash-rich hydrocarbons, cooling the crude gas in a radiant cooler and then in a convection cooler, wet the crude gas. The washing water, which has been washed with water in the separator and, optionally, combined with the aqueous phase of the radiant cooler, is left in a separating device with a residue essentially containing carbon, metals and / or metal compounds and water. , And production of synthesis gas by separating it with purified water as a filtrate, and cooling the crude gas saturated with steam to separate the water and form a solids-free synthesis gas. Solved by the method. This method treats the filter residue with an acid, optionally after partial dehydration in the separating apparatus,
The resulting metal salt solution is withdrawn and the residual carbon particles are sent back for the partial oxidation.

[0007]

The process according to the invention starts, inter alia, from ash-rich hydrocarbons as feedstock for its synthesis gas generation. Preferably, various heavy oils, i.e. liquid hydrocarbon mixtures which occur as high boiling fractions during the distillation of petroleum, and bitumen, i.e. semi-solid to solid high molecular weight hydrocarbon mixtures, and various emulsions made from bitumen are mentioned. Used. Heavy oils, such as bitumen, contain vanadium, nickel, among others, as ash-forming components, and, in addition thereto, compounds of iron, chromium and molybdenum in amounts of about 1 to 2500 ppm as metals. Under such circumstances, it is necessary to consider those raw materials rich in metal to obtain hydrocarbons having different boiling ranges such as gasoline, kerosene, and gas oil. As the trend increases, so does the ash content of the heavy oil,
And new sources of raw materials are continuously developed to produce syngas, with the result that bitumen belongs to this.

1200 to 15 from the gasification reactor
The crude gas emerging at a temperature of 00 ° C. contains, in addition to traces of carbon particles, various metals and metal compounds in liquid or solid form. This is first of all the temperature at which the impurities of these metals solidify in the radiant cooler, ie 500
To 1000 ° C. The solid particles are only slightly separated in the water vapor of the radiant cooler and are carried away therefrom. A temperature limited by the pressure of the produced process steam (eg 250 to 300)
For further cooling to (.degree. C.), the crude gas containing the still remaining part of the fine metal particles and part of the carbon particles is introduced into a convection cooler.

An almost complete separation of these solid substances is carried out by washing this gas with water. The above-mentioned substeps of the process can be carried out using wet separators of the prior art as is known. In particular, packed towers have been demonstrated that allow water to flow down, which can optionally also be used in combination with a venturi scrubber. It is necessary to preheat the wash water, which is inherently circulated, advantageously by heat exchange with the wash water used for washing.

Following this gas scrubbing, the two material streams may be further processed individually. That is, an aqueous phase (washing water) containing the solid substance and a gas phase containing no solid substance but containing a large amount of water vapor.

The cleaning water used for cleaning is heated by the heat transferred from the crude gas. It is therefore heated from the sump of the scrubber, preferably after combining with the water of the sump of the radiant cooler, and after depressurizing in the intermediate reservoir and separating the gas released by the depressurization. It is guided through the exchanger and then fed into the separating device. The separating device is usually a filter, preferably a chamber filter or a membrane filter press, which has a large filtration area and a sufficient storage volume for the solid phase and is equipped with an airtight plate gasket. This is used to separate the solid and aqueous phases. The carbon particles contained in the wash water then act as a filter aid and promote the separation of the metals and / or metal compounds. Very fine particulate carbon is particularly effective. Such carbon particles have a partial oxidation of the hydrocarbon, for example, European Patent E.
It is obtained with a burner specially constructed according to the teachings of P-B1-0095103 and incorporating certain method measures, and when a sufficiently thick carbon deposit is formed on the filter. The latter can be ensured in a manner familiar to the person skilled in the art by ensuring that no wastewater is withdrawn during the start-up of the filtration process. When this is done, the filtrate contains less than 0.5 mg / l nickel. It can therefore be discharged directly as wastewater and it is unnecessary to revert to the gasification process, as described in DE-A-4117266.
Guarantee against leakage of solid material, eg due to filter failure, is achieved by directing the filtrate through a small auxiliary filter designed only for the wastewater. In this way, the wastewater is withdrawn in such an amount that the chlorine content of the wastewater, which depends on the chlorine content of the heavy oil, is kept within the limits conditioned by the structural material. With normal quality oils and materials of construction, this is only a small fraction of the total wastewater, which consists essentially of practically metal-free process condensate.

The filtration residue contains carbon particles, metal and / or metal compounds in concentrated form and water. For ease of handling, it can also be partially dewatered, for example by passing compressed air through it, before further processing. According to the invention, this residue is then treated with an acid in a separator to elute the metals and metal compounds.

The treatment in this separation unit allows the harmful waste substances, such as hydrogen sulphide, which are formed in the presence of metal sulphides, to be separated from the various gasification reactions thereof, rather than in a separate work process. Together with the waste substances, it can be reliably converted into environmentally neutral products, for example by the Claus method.

Extraction of the metal and / or metal compound is carried out using an acid. Suitable for this acid treatment is hydrochloric acid,
Not only inorganic acids such as sulfuric acid or nitric acid but also various organic acids, especially low molecular weight monocarboxylic acids such as formic acid, acetic acid or propionic acid, preferably particularly easy to handle and harmful to ordinary equipment materials It is acetic acid with no. These acids are used as aqueous solutions, and acetic acid is used, for example, in concentrations of 1 to 50% by weight of the solution. Although the extraction process can be carried out at room temperature, in order to accelerate the reaction, the temperature is in the range of 20 to 80 ° C,
Above all it is recommended to work at elevated temperatures in the range of 40 to 60 ° C. Furthermore, it is recommended that the acid be circulated in order to reduce the required amount and obtain a highly concentrated metal salt solution. The metal salt solution remaining in the filter cake is removed in a manner known to those skilled in the art by rinsing with water, and the rinse is added to the original metal salt solution. Extract the combined metal salt solution,
It can then be post-treated according to the respective application. The solid material remaining after extraction of the metal consists almost exclusively of carbon in the form of carbon particles. This can be mixed with heavy oil and returned to the gasification reaction. The metal components remaining in this solid substance are thereby once more exposed to the reaction conditions, whereupon they are in the form of sulphides which are soluble in acetic acid.

The solid-free gas from the gas scrubber is saturated with water vapor. It is cooled in one or more stages, preferably under relatively low pressure stage process vapor recovery, in order to recover the available heat. A second water fraction is produced within the framework of the whole process, which is 0.1 mg.
It contains metals and / or metal compounds in an amount less than 1 / l. This wastewater can be immediately fed to a water treatment plant to separate volatile compounds such as hydrogen sulphide, hydrogen cyanide and ammonia which are present in their bound or free form.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings show in detail one of the embodiments of the working method according to the invention. In reactor 1, a fuel such as heavy oil is reacted with water vapor and oxygen to form a crude syngas (crude gas), which is precooled in a radiant cooler 2 and then It is introduced into the convection cooler 3. The various solid substances separated in the radiant cooler 2 are suspended in water and sent to the storage tank 9 via the valve 4. The crude gas still containing solid particles is the wet separator 5
After being washed in and cooled in the cooler 6, it is discharged from this device via conduit 21. The water condensed from this gas is intermediately stored in a storage tank 7 and fed via conduit 22 to a water treatment device or pump 8 back into the process. The washing water of the wet separator 5 containing the solid substance suspended therein is the valve 4
It is collected in the reservoir 9 as well as the solid substance suspension from. From there, the combined and degassed water stream reaches the filter press 11 by the pump 10. Obviously, it is also possible to provide two filter presses operating in alternation. The filtrate, which is the aqueous phase free of solids, is collected in a reservoir 15 and sent back to the process via pump 16 or is discharged via auxiliary filter 17 and conduit 22. After the filtration residue in the filter press 11 has been dewatered, it is treated with acid which reaches the filter press from the reservoir 18 via the pump 20 and is rinsed with water.
The filter residue after extraction is thixotropic. It is discharged into a collecting trough 12 equipped with a stirrer to make it flowable, and the suspension pump 13 and the conduit 14
Can be recycled to the reactor via. Gaseous waste such as hydrogen sulphide, along with other gaseous by-products produced during its gasification process, is fed via conduit 23 to the coupling processor.

Several variants of the working mode described above are possible, adapted to the relatively low content of heavy metals in the raw material. That is, for example, extraction can be initiated at a suitably selected cycle to increase the content of solid material to a desired value.

[Brief description of drawings]

1 is a flow sheet of one embodiment of an apparatus for carrying out the method of the present invention.

[Explanation of symbols]

 1 Reactor 2 Radiant Cooler 3 Convection Cooler 4 Valve 5 Wet Separator 6 Cooler 7 Storage Tank 9 Storage Tank 11 Filter Press 12 Collection Trough 13 Suspension Pump 15 Storage Tank 17 Auxiliary Filter 18 Storage Tank

Claims (5)

[Claims] 1. The carbon used as the hydrocarbon is 0.
Under the formation of a crude synthesis gas containing 1 to 0.3% by weight of carbon particles, liquid, semi-solid or solid hydrocarbons, especially hydrocarbons rich in ash, are partially oxidized, and this crude gas is The wash water, cooled in a radiant cooler and then in a convection cooler, the crude gas is washed with water in a wet separator and optionally combined with the aqueous phase of the radiant cooler. In a separation device into a residue essentially containing carbon, metal and / or metal compounds and water, and purified water as the filtrate, and cooling the crude gas saturated with steam. In a process for the production of synthesis gas by separating water and forming a solids-free synthesis gas, the filter residue, if desired after partial dehydration in the separating device, And remove the resulting metal salt solution And, and a method of the residual carbon and returning the feed for the partial oxidation. 2. The method according to claim 1, wherein the filtration residue is treated with acetic acid. 3. Acid treatment from 20 ° C. to 80 ° C.
Process according to claim 1 or 2, preferably at a temperature of from 40 ° C to 60 ° C. 4. The method according to claim 1, wherein the separating device is a filter press. 5. The method according to claim 1, wherein the partial dehydration of the filtration residue is carried out with compressed air.