DE4329462A1 - Process for reducing the formation of coke when used plastics are used in the refinery - Google Patents

Abstract

Thermally pretreated used plastics or mixtures of used plastics can be recycled together with petroleum distillates in refinery plants, such as crackers, visbreakers and hydrogenation plants. A disadvantage is the formation of coke, which occurs even at low temperatures and results in a shortening of the operating times. The process according to the invention is based on thermal degradation of the plastic content in the extruder without addition of the active gases, a progressive temperature profile up to a maximum of 475 DEG C being set in 2/3 of the effective extruder length and a degressive temperature profile up to from 300 to 380 DEG C being set in the final 1/3 of the effective extruder length, and a coke-reducing additive known per se being metered in at the end of the extruder head or before a downstream static mixer in an amount whose concentration after the subsequent mixing-in of the pretreated used plastic content in amounts of up to 20% by weight into the refinery stream is between 10 and 200 ppm in the total feedstock for the petroleum processing step. The pretreatment of the used plastics can be carried out either as an integral step in the refinery plants or externally.

Description

There are various methods for the treatment of old art substances or mixtures of old plastics has been proposed to the then pretreated products in the bypass in refinery use method.

Thus, in DE-OS 40 17 089 for the production of Synthe segas and analogue in DE-OS 40 29 880 for fuel gas beat the plastic waste by adding reactive Gases, such as oxygen, air, possibly hydrogen and water steam or water, the moistening of the feed material was given at elevated temperature by degradation of the poly so far as to liquefy them with conventional Devices are injected into combustion chambers or reactors can.

These methods have the disadvantage that they due to the Zu tion of reactive gases, eg. As in oxygen, to products which are not suitable for all uses or lead to significant corrosion erosion rates. At one set of precursors so prepared in a laboratory visbreaker showed intolerable coke formation rates.

In DD-PS 2 00 891 a method for the production of Koh hydrocarbons from polyolefins, in which the Polyolefins dissolved in liquid hydrocarbon mixtures become, the received Mineralölähnliche pumpable solution closing a thermal treatment at temperatures  100 ° C is subjected and the resulting mixture either a usual in the mineral oil industry Weiterver subjected to evaluation or without further treatment energetic use, preferably as fuel oil supplied becomes.

The method has the disadvantage that on the one hand only low poly olefin shares are immiscible, otherwise the viscosity too rises rapidly, and on the other hand, an unreasonably high coke formation both in thermal cracking and in the zwi switched hydrogenation of up to 180 ° C boiling An parts occurs.

EP 0 236 701 discloses a process for thermal pretreatment ment of synthetic organic wastes, in which in the presence of hydrogen or inert gas in a tempera range of 75 to 600 ° C, a pressure range of 1 to 600 bar and a residence time of 1 minute to 6 hours ge is working. The addition of protic solvents is also disclosed in this patent as well as the addition of grinding oil and catalysts.

Tables 6 and 8 summarize experimental results, in the thermal pretreatment without the addition of Anreib oils were obtained. It was heated to temperatures of 350 to 470 ° C worked. Subsequent investigations by the applicant of the However, EP 0 236 701 showed that in this temperature range undesirable coke formation occurs, the coke partially coarse-grained accumulates and clogs and deposits in the entire system can lead.  

The Applicant of o. G. EP has surprisingly found that when using synthetic organic waste, the coke education can be avoided or largely avoided can syntheti by a method for thermal treatment shear, organic waste, characterized in that Waste at a temperature of 220 to 350 ° C and a pressure from 10 mbar to 1 bar with a residence time of 0.5 to 24 Hours are subjected (DE-OS 41 14 434).

Also by adding certain additives with or without mash Oil can be favored the thermal treatment. As Addi For example, one or more connections can be active the group phenols, sulfur compounds, alcohols, amines and Add water. The splitting thermal treatment can be carried out batchwise or continuously. For the continuous driving, for example, a Stirring cascade be used. In discontinuous driving wise, with the help of a Vorbehälters the setting of Spalttemperaturen and residence time made particularly favorable. After reaching a certain viscosity can then by Lowering the temperature by about 50 K further cleavage be interrupted or slowed down.

The method can also be used for thermal cleavage very low temperatures, the formation of coke is not full constantly prevent. At the low temperatures but will disadvantageous accepted that the dismantling times unacceptable high (up to 24 hours). Through the process, the Coke formation at higher temperatures, as in the petroleum processing are common, according to EP 0 236 701 not avoided become.

It was therefore the task of developing a method in the old plastics or Altkunststoffgemische continuously are degraded in the molar mass, which when used in the earth oil processing stage to a substantial reduction of Coke formation, at least to the comparable value of pure petroleum intermediates.

The problem has been solved by a method for reduction Coke formation when using old plastics in the Raffi nerie, including the thermal degradation of old art share of material by means of shear and elevated temperature in an extruder, with no reactive gases added, by according to the invention first, the old plastics or Alt mixed plastics at 2/3 of the effective extruder length progressive temperature profile up to max. 475 ° C and on the last 1/3 of the effective extruder length a degressive Tem temperature profile be subjected to 300 to 380 ° C and am End of the extruder head or before a downstream sta Mixers are known per se for coke formation Adding additive is added in an amount that its Concentration after the subsequent meddling of the so before treated waste plastics in amounts of up to 20 Mass% in the refinery stream in the total feed of the Petroleum processing level is between 10 and 200 ppm.

As known additives for reducing coke formation become polar alkyl derivatives and / or their mixtures with amines used. In particular, the antifoulant additives are suitable Fa. German Nalco-Chemie GmbH, Frankfurt a. Main.  

It has been shown that it is advantageous to use the additive in high-boiling aromatics or alkylaromatics dissolved or in the respective petroleum intermediates for petroleum processing level dissolved at the end of the extruder head or before one after metered switched static mixer.

According to the method of the invention, the entire procedural unit of waste plastics processing in a refinery integrated unit and the processed waste plastic product flow as a bypass into the main stream of petroleum processing be mixed in the processing stage.

But it is also possible, the entire processing unit externally install and the product obtained in a suitable Form, preferably as granules, to assemble and over a melting unit with integrated melt pumps as Bypass to be incorporated into the refinery stream.

It is also possible after the invention Aufberei processing of waste plastics or waste plastics mixtures Melting in a known manner directly or after a Be to filter calm route to fine-powdered mineral additives, Weed out pigments or unmelted fractions.

As waste plastics or waste plastic mixtures in the sense of Invention can be after one or more times use in the commercial sector resulting products, such. Eg country plastic films, transport packaging, canisters, hollow bodies, Use bottles, etc., or the per-household waste products, preferably the floating fraction (products with a Density <1 g / cm³). But it is also possible to get products from the Production (defective batches, arrival and changeover products for varieties change, samples from process and analytical equipment, etc.) or  the processing (incorrect batches, Spritzgußangüsse etc.) einzu put. It is expedient, the feedstock to a Grain size from 3 to 8 mm to bring.

The extruders are both single-screw and twin-screw extruders, preferably co-rotating twin-screw extruder, use bar, bring the appropriate shear forces and invented allow the degradation temperatures according to the invention.

It was surprising that with the addition of known Addi A strong influence on their effect from the place of Zu was to be recorded.

The invention will be apparent from the following embodiments explained in more detail.

Example 1

For the investigations a laboratory visbreaker was available. The apparatus is equipped with a temperature-controlled storage vessel for Equipped with feedstock mixtures. through a metering pump, the product is supplied to the visbreaker. This consists of a preheating zone (4.5 m capillary tube, 4 mm inner diameter) and the actual reaction zone (11 m Capillary tube, 4 mm inner diameter). The pressure maintenance he follows via a control valve.  

A mixture of vacuum residue of the specification

Density (130 ° C), g / cm³ 0.932 Viscosity _kin. (130 ° C), mm² / s 136 nC₅-asphaltene, mass% 12.4 colloidal stability (after Neste Oy) 4.2 Elemental composition,% @ C 85.8 H 10.1 N 0.20 O 0.747 S 3.15 Cl 0,003

and 7.15 mass% of a waste plastic mixture (65% LDPE, 30% HDPE, 5% PP) in a co-rotating twin screw extruder with a screw diameter of 53 mm and one effective screw or extruder length L of 42 D under Ein effect of a progressive / declining temperature profile (Tem maximum temperature at 28 D = 420 ° C, temperature at the end of the Extruder = 380 ° C) had been thermally pretreated, with the properties

Molecular weight M _W , g / mol 38,400 Viscosity (230 ° C), mm² / s 3 670 Ash, mass% 0.6 Gel content, mass% 0.8

is guided into the visbreaker and under known conditions (T = 475 ° C, t = 12 min) implemented. Inserting coke deposit is due to a reduction in the heat transfer (change in the Heating rate) and increasing pressure drop in Visbreaker recognizable. After 144 hours of operation, the pressure drop of the zone was not more acceptable.  

example 2

The experiment of Example 1 was repeated. The feedstock stream of visbreaker was used to prevent coke deposition a mixture of neutralized amine, alkyl phosphates and poly ester dissolved in high-boiling aromatics (Nalco 5272) in one Amount added that there were 80 ppm in the total stream. After 260 h The duration of the visbreaker was the same as in Bei reached game 1.

example 3

The waste plastic mixture used in Example 1 was modified by analogous degradative degradation as follows:
After reaching a temperature of 380 ° C, the melt between the extruder and a downstream static mixer 1000 ppm of the mixture of neutralized amine, alkyl phosphates and polyester, dissolved in vacuum residue, were mixed. The thus modified batch material was metered directly into the product stream of the visbreaker. A mass ratio of batch product to vacuum residue of 1: 12 was set, resulting in a waste plastic content of 7.6% by mass in the total flow. The further procedure corresponded to the conditions of Example 1. The limit state regarding coke deposition was reached after 320 hours of operation of the visbreaker.

example 4

Analogously to Example 3, a batch material from degraded Old plastic and dissolved in vacuum residue mixture of new tralized amine, alkyl phosphates and polyesters. This product was formulated as granules. The granules  was in the product via a melting and dosing unit stream of visbreaker dosed and under conditions such as at game 1 to 3 implemented. The ratio of batch to vacuum back stood again 1: 12. The pursuit of pressure drop and heat transfer in the visbreaker led to the same He result as in example 3.

example 5

From the thermally pretreated used in Example 1 Waste plastic and hydrosalt paraffin of the boiling range 325 to 540 ° C, a 1: 1 mixture was prepared.

This product mixture was in the ratio 1: 4 of Konfek tion zone of a laboratory cracker, containing hydrosoluble wax is fed, fed. The total mixture, which is 10% by mass contains degraded waste plastic, then at 800 cracked to 870 ° C. Coking in the fracture zone can be recognized by an increase in the outlet temperature. The Trial was stopped after 105 h.

example 6

The experiment of Example 5 was repeated with the sub decided that the Hydrospaltparaf supplied to the laboratory cracker fin mainstream a mixture of phosphoric acid alkyl ester and alkylamine in high boiling alkyl aromatics (Nalco 5270) in an amount of 1200 ppm based on the 1: 1 mixture of Altkunststoff and Hydrospaltparaffin is added. The Be operating time of the cracker extended in this case 163 h.  

example 7

The experiment of Example 5 was repeated with the sub that the old plastic used at the end of the Ex truderkopfes at the same time as mixing with Hydrospaltparaf fin 1200 ppm (based on the 1: 1 mixture of waste plastic / hydro split paraffin) of a mixture of phosphoric acid alkyl ester and alkylamine in high boiling alkyl aromatics (Nalco 5270) to be worked. The operating time of the cracker extended with twice the operating time according to example 5. In addition, it was found that the scheduled Coke was easier to remove.

Claims (6)

1. A method for reducing the formation of coke in the use of waste plastics in the refinery involving the thermal degradation of the Altkunststoffanteils with the help of shear and elevated temperatures in an extruder, with no reactive gases are added, characterized in that initially the waste plastics or Altkunststoffgemi cal on 2/3 of the effective extruder length a progressive temperature profile up to max. 475 ° C and on the last 1/3 of the effective extruder length a degressive temperature profile up to 300 to 380 ° C are subjected and at the end of the extruder head or before a downstream static mixer a per se known coke-reducing additive is added in an amount, that its concentration is between 10 and 200 ppm after the subsequent incorporation of the thus-reserved old plastic fraction in quantities of up to 20% by weight into the refinery stream in the total feed of the petroleum-processing stage. 2. The method according to claim 1, characterized in that as per se known coke-reducing additive polar alkyl derivatives and / or mixtures thereof with amines. 3. The method according to claim 1 and 2, characterized in that the additive in high-boiling aromatics or alkylaromatics ge releases at the end of the extruder head or in front of a downstream one static mixer is metered. 4. The method according to claim 1 and 2, characterized in that the additive dissolved in the respective petroleum intermediate for the petroleum processing stage at the end of the extruder head or is added before a downstream static mixer.   5. The method according to claim 1 to 3 or 4, characterized net, that the entire process unit of waste plastic processing is integrated into the refinery unit and the processed waste plastic product stream as a bypass in the main stream of petroleum processing stage is mixed. 6. The method according to claim 1 to 3 or 4, characterized net, that the entire process unit of waste plastic externally installed, the product obtained in a suitable form, preferably as granules, confection and a melting unit with integrated Melt pumps as a bypass in the refinery stream eingear is processed.