WO2017134591A1

WO2017134591A1 - Process for the recovery of metals from an organic matrix

Info

Publication number: WO2017134591A1
Application number: PCT/IB2017/050560
Authority: WO
Inventors: Felicia Massetti; Madardo PINTI; Maria Ilaria Pistelli
Original assignee: Eni S.P.A.
Priority date: 2016-02-04
Filing date: 2017-02-02
Publication date: 2017-08-10
Also published as: ITUB20160183A1

Abstract

The present invention relates to a process for the recovery of metals contained in the organic phase of a bitumen produced in a petrochemical process and comprises the following steps: a fast pyrolysis step under certain temperature conditions that generates synthesis gas and a carbon residue containing the metals (in the form of metal compounds); an oxidation step wherein the carbon residue is oxidized at a controlled temperature forming a solid phase (ash also containing the metal oxides for recovery) and a gaseous phase (flue gases).

Description

"PROCESS FOR THE RECOVERY OF METALS FROM AN ORGANIC MATRIX"

Description

The present invention relates to processes for the treatment of refinery residues, by exploiting their energy in streams rich in carbon compounds and metal compounds. More in particular, the present invention relates to a process for the recovery of metals contained in bitumens of petrochemical origin, particularly for the recovery of metals contained in the residues deriving from hydrocracking processes, such as the Eni Slurry Technology (EST) process owned by Eni S.p.A.

In particular, the process described and claimed may be applied for the recovery of metals contained in the organic phase of a bitumen. In particular, within the scope of EST technology, said process may be applied for the recovery and recycling of catalytic metals of the hydrocracking process, such as molybdenum and vanadium. The process according to the present invention allows the carbon fraction contained in refinery residues to be completely oxidized and the metals, such as molybdenum and vanadium (in the form of metal compounds) to be concentrated, so as to be sent for subsequent recovery.

For the purpose of this text, all the operating conditions mentioned in the text must be considered as preferred conditions even if this is not specifically stated.

For the purpose of this text the term "comprise" or "include" also comprises the term "consist in" or "essentially consisting of.

For the purpose of this text the definitions of the intervals always comprise the extremes of said intervals, unless specified otherwise.

In the state of the art, apparatuses and processes are known for the recovery of elements or of metal oxides from organic and inorganic matrices; processes of a chemical nature or based on pyrometallurgy, hydrometallurgy and roasting (such as the Nesa process). The chemical processes may imply the onset of further problems connected with the use of substances that could create chemical derivatives that are environmentally difficult to dispose of.

Patent US 7,037,871 describes a process for regenerating a hydrocarbon conversion metal catalyst with ozone, preferably at a temperature comprised between 20°C and 250°C, with a partial pressure of the ozone up to 1 atm and with a molar concentration of ozone comprised between 0.1% and 5%.

Patent US 7,368,409 describes a process for regenerating a solid catalyst or a solid adsorbent where the catalyst or the adsorbent, containing an amorphous or zeolitic support, is used in the form of a bed moving in a regeneration zone, comprising at least one heating step in presence of a reducing atmosphere.

Patent US 4,551 ,437 describes a process for regenerating a solid catalyst, wherein said solid circulates continuously in a chamber having certain characteristics and on which a vibration is imparted such as to set the catalyst in motion. While the solid circulates the catalyst is subjected to a thermal treatment through electromagnetic radiations with a wavelength comprised between 0.38 μιη and 50 mm.

In order to obtain a metal of a particular purity, industrial technologies such as pyrometallurgy and hydrometallurgy processes are solutions that require a complex series of operations, in particular where these two technologies are in series: fusion of a solubilizing metal, almost always copper or iron, subsequent treatments in selective acids for the purification of the compound, each with its own typical efficiency. As well as being particularly costly, these processes often have low overall yields.

NESA technology, which is used for the recovery of molybdenum from minerals, poses problems connected with adhesion and the transport of bitumen from EST treatment, inside the furnace. The solutions designed to solve the problem, such as the adhesion of alumina balls able to transport the material into the subsequent reaction plates of the NESA furnace, are particularly costly and not very efficient, having a treatment capacity of less than 0.9 kg/m²h at the end of the process. The material obtained then requires a further purification and chemical treatment step.

EP 1612482 describes a device for eliminating waste containing a cylindrical and rotating chamber into which the waste is fed. The fuel is injected into the chamber together with oxygen and air. The agents supporting the combustion are injected through a first and a second set of nozzles. Combustion or gasification takes place in the chamber which generates inert solid material and gaseous material, which are discharged from the device.

WO 2011/007231 relates to a continuous process for the thermal treatment of refinery sludge comprising different steps. The sludge is dried at a temperature comprised between 110°C and 120°C. The dried sludge is gasified at a temperature comprised between 750°C and 950°C for a period comprised between 30 minutes and 60 minutes in presence of a gas containing oxygen and water vapor, producing synthesis gas and a solid residue. The synthesis gas is combusted at a temperature comprised between 850°C and 1200°C and the combustion products are recirculated to the drying and gasification step. The solid residue is made inert at a temperature comprised between 1300°C and 1500°C by vitrification.

The solutions proposed in EP 1612482 and WO 2011/007231 still have numerous unsolved problems, such as chemical components that are difficult to manage, a high number of successive reaction steps for obtaining material with the right degree of purity, high quantities of flue gases generated by the treatment, high operating times, low flexibility and system complexity. The drawbacks and limitations of the prior art described above, are overcome by the process described and claimed in the present text. Said process is able to increase the treatment capacity of a bitumen and preferably of a bitumen produced with an EST hydrocracking process, generating low levels of flue gases. Furthermore, said process is able to maximize the contact between the material to be purified and the gas flow necessary for the removal of the metals contained therein.

The invention is therefore a process for the recovery of metals contained in the organic phase of bitumens generated in petrochemical processes, preferably in hydrocracking processes. In particular molybdenum and vanadium, present as elements or as compounds, contained in the organic phase of a bitumen, are recovered. Said process comprises the following steps:

subjecting the bitumen, said bitumen preferably being produced with an EST process, to a first phase of fast pyrolysis with an increasing temperature ranging from 50 to 100°C/s, preferably between 80 and 100°C/s, more preferably from 90°C/s to 100°C/s, producing synthesis gas and a carbon residue containing carbon and metal oxides, and

subsequently, subjecting said carbon residue to oxidation with a stream containing at least 40% by volume of oxygen, preferably at least 60% by volume of oxygen, at a controlled temperature ranging from 300°C to 650°C, even more preferably from 550°C to 630°C, forming a solid phase containing metal oxides constituting the ashes, and a gaseous phase typically containing nitrogen and carbon dioxide, also referred to as flue gas.

Advantageously, the synthesis gas produced can be exploited for the self-sufficiency of the process and for better heat control.

Advantageously, fast pyrolysis allows a low degree of graphitization of the treated bitumen and a larger reactive surface area to be obtained.

The performance of the oxidation reaction with high oxygen concentrations, greater than or equal to 40% by volume, enables the reaction speed to be increased by mass action (high oxygen concentration) minimizing particle drag.

The performance of the oxidation reaction at temperatures less than 650°C allows a better yield of metals such as molybdenum and vanadium to be obtained.

With respect to known thermal processes, such as the NESA pyro-gasification process, the process described and claimed is simpler to apply since it does not require any sieving, pelletizing, adhesion to spherical substrates or preliminary grinding processes. The bitumen is therefore not pre-treated but is fed directly to the pyrolyzer.

Advantageously, owing to the intrinsic characteristics of the method with which the rotating drum furnaces are loaded (using screws, pumps or silos according to the initial nature of the material) and owing to the actual characteristics of this type of reactors in which the material advances with rotation, said process can treat solids with a wide range of particle sizes, morphological characteristics and load viscosities.

Advantageously, said process allows lower off-gas volumes to be treated, has a higher specific efficiency in terms of quantity of carbon removed (kg/m²h), and lower investment and operating costs.

Further objects and advantages of the present invention will appear more clearly from the following description and appended figures, provided by way of non-limitative example, which represent preferred embodiments of the present invention.

Figure 1 and Figure 2 illustrate preferred embodiments of the process according to the present invention, according to a block diagram.

Detailed description.

The detailed process is now described for the recovery of metals contained in the organic phase of bitumens generated in petrochemical processes, preferably in hydrocracking processes. In particular, with the process described and claimed, the metals molybdenum and vanadium contained in the organic phase of a bitumen are recovered.

Bitumen is defined as a stream coming from petroleum or its derivatives that contains hydrocarbons, carbon and metal residues, such as sludge streams coming from catalytic slurry phase hydrocracking processes, such as those of the EST processes. The metals contained in the bitumen to be treated may be molybdenum, vanadium, nickel, chromium, silicon and iron.

Molybdenum, vanadium, nickel and chromium are considered precious metals, while silicon and iron are considered impurities already contained in the raw material, bitumen. The metals contained in bitumens may come from the catalyst used in catalytic slurry phase hydrocracking processes, or may be already contained in the loads subjected to said hydrocracking process. Said metals may be dispersed, in the form of more or less complex compounds, aggregates and particles having dimensions normally less than a millimeter. The dimensions in the present text indicate the mean diameter which is measured with known methods in the state of the art.

In a first step the bitumen, preferably bitumen produced with an EST process, is subjected to fast pyrolysis where the temperature increases at a speed that varies in the range from 50°C/s to 100°C/s producing synthesis gas and a carbon residue containing carbon and metal oxides. The first pyrolysis step may be performed at a temperature comprised between 300°C and 650°C, even more preferably from 550°C to 630°C.

The first pyrolysis step must be performed with a heating speed that ranges from 50°C/s to 100°C/s, for the purpose of obtaining a low degree of graphitization of the bitumen treated and a larger reactive surface area. The temperature, during the fast pyrolysis, preferably increases at a speed comprised between 50°C/s and 100°C/s, more preferably between 90°C/s and 100°C/s.

Subsequently, said carbon residue is subjected to oxidization, where the oxidizing stream contains at least 40% by volume of oxygen, preferably at least 60% by volume of oxygen. Preferably, the oxidation reaction is performed at high oxygen concentrations, preferably such as 21% to 45% by volume, more preferably from 35% to 40% by volume. Such oxygen concentrations have the purpose of increasing the reaction speed by effect of mass and reducing the quantity of comburent substance with respect to the same value of oxygen obtained with air and therefore, with the same flue gas outlet section, reducing the outlet speed of the flue gases produced so as to minimize particle drag.

Oxidation must take place at a controlled temperature, maintained at a value comprised between 300°C and 650°C, even more preferably from 550°C to 630°C, temperatures at which the best reaction speeds and the best recovery yields of metals are obtained, in particular molybdenum and vanadium.

With oxidation, a solid phase is formed containing metal oxides, constituting the ashes, and a gaseous phase containing nitrogen and carbon dioxide, referred to herein as flue gas.

Preferably, after the pyrolysis step, the carbon residue may be ground in a mill, placed at the outlet of the pyrolysis section, with the aim of further increasing reactivity in the subsequent oxidation step.

To guarantee a temperature greater than or equal to 650°C in the oxidation step, a cooling system must be provided able to dispose of the heat generated, such as through the introduction of a steam lance.

The synthesis gas produced during the pyrolysis step may be totally oxidized in the combustion chamber and the flue gases produced may be in part used to thermally sustain the pyrolysis step. Alternatively, the synthesis gas, or its surplus with respect to self-sufficiency, may be sent to recovery and exploitation sections. All of the flue gases coming from the oxidation of the synthesis gas and from the oxidation of the carbon residue, before being sent to a treatment system, may be used for producing steam in a boiler, guaranteeing the exploitation of their energy. Part of the synthesis gas may also possibly be recovered as fuel.

Figure 1 illustrates a preferred embodiment of the process according to the present invention. A sludge current (1), or bitumen, is sent to a pyrolysis furnace (A) producing synthesis gas (2) and a carbon residue (3). The carbon residue is sent to a mill (B) and then fed to an oxidation furnace (8,C) to which air or oxygen-enriched air are also fed, generating flue gases (6) and a solid phase (7) which contains ashes and metals. The synthesis gas may be sent to a combustion unit (E) to which air is fed. The synthesis gas may even be sent to a recovery section (D). Part of the combustion flue gases (4) produced by burning the synthesis gas may be used for thermally sustaining the pyrolysis step. Another part of the flue gases (9) may instead be sent to a flue gas treatment section (F) to which the exhaust flue gases from the pyrolyzer are also fed.

After oxidation of the carbon residue, the flue gases (6) are also sent to a ceramic filter (G) and subsequently to a flue gas treatment section (F). Subsequently, the metals contained in (7) are separated from the ashes.

Below are some examples for better understanding of the invention and within the scope of application, although not constituting in any way a limitation to the range of the present invention.

Example 1:

Table 1 shows the elements contained as a % in the bitumen produced in the Sannazaro EST process (BEST) which is indicated as "cake EST snz".

Table 2 shows the metal compounds of the bitumen produced in the Sannazaro EST process (BEST).

Table 1

With reference to Figure 2, the process for recovering the metals contained in a bitumen from the petrochemical industry, envisages the following sections:

1 pyrolyzer (A),

1 blade mill (B),

1 combustion unit for treating the flue gases (F),

4 oxidizers (C1 , C2, C3, C4) in parallel

1 settling chamber (H).

Two loads of EST bitumen (cake) equal to 2000 kg/h and 1500 kg/h were considered, respectively. Tables 4 and 5 show the balances when the load is equal to 2000 kg/h and when the load is equal to 1500 kg/h.

Table 4

Nm³/h Nm³/h

Table 5

Pyrolysis is performed at 600°C; the radiating tube within the pyrolyzer operates at

750°C; the flue gas combustion unit operates at 950°C. The flue gases leaving the process are at 779°C and have the following composition:

0₂ = 10.8%

S0₂ = 4970 mg/Nm³

NOx = 433 mg/Nm³

To calculate the balance, the limits for the emissions of S0₂, NO_x, NH₃ and powders mentioned in table 4 were considered.

Table 4: Limits for emissions of S0₂, NO_x, NH₃ and powders

LIMITI EMISSIONI (rif . 3% 0₂)

Concentrazione S0₂ 30 mg/Nm³

ConcentrazioneNOx 70 mg/Nm³

Concentrazione NH₃ 12 mg/Nm³

Polveri 9 mg/Nm³

Claims

Process for the recovery of metals contained in the organic phase of a bitumen produced in a petrochemical process; said process comprises the following steps: subjecting the bitumen to a first phase of fast pyrolysis with an increasing temperature ranging from 50 to 100°C/s, producing synthesis gas and a carbon residue containing carbon and metal oxides, and

subsequently, subjecting said carbon residue to oxidation with a stream containing at least 40% by volume of oxygen, preferably at least 60% by volume of oxygen, at a controlled temperature ranging from 300°C to 650°C, forming a solid phase containing metal oxides constituting the ashes, and a gaseous phase typically containing nitrogen and carbon dioxide, also referred to as flue gas.

Process according to claim 2 wherein the pyrolysis step is conducted at a temperature ranging between 550°C and 630°C.

Process according to any one of claims 1 to 2 in which the temperature, during the fast pyrolysis, increases with a speed ranging between 80°C/s and 100°C/s.

Process according to any one of claims 1 to 3 in which the oxidation reaction is conducted at oxygen concentrations ranging from 21% to 45% by volume.

The process according to claim 4 wherein the oxidation reaction is conducted at oxygen concentrations ranging between 35% and 40% by volume.

Process according to any one of claims 1 to 5 in which the organic phase of the bitumen contains Molybdenum, Vanadium, Nickel, Chromium, Silicon and Iron. Process according to any one of claims 1 to 6 wherein after the step of pyrolysis, the carbon residue is ground in a mill, placed at the exit of the pyrolysis section. Process according to any one of claims 1 to 7 in which the synthesis gas produced is totally oxidized in the combustion chamber and the fumes produced are in part used for the thermal maintenance of pyrolysis phase.

9. Process according to any one of claims 1 to 8 in which the synthesis gas can be sent to recovery and development sections, or is recovered as a fuel.

10. Process according to any one of claims 1 to 9 in which the fumes coming from the oxidation of the synthesis and oxidation of the carbonaceous residue gases are used to produce steam in the furnace.