RU2485400C1 - Method of decontaminating hydrocarbon-containing wastes with simultaneous deposition of dissolved metal salts and apparatus for realising said method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of decontaminating hydrocarbon-containing wastes, involving oxidising and compressing the wastes to pressure P>PcrH₂O and then feeding into a reactor. The method is realised by oxidation in the medium of supercritical water at temperature T>TcrH₂O in the presence of an oxidant and is characterised by that the wastes are heated to temperature T>TcrH₂O by a recirculating supercritical solution of the decontaminated wastes directly in the reactor (where PcrH₂O is the critical pressure of water - 218 atm, TcrH₂O is the critical temperature of water - 374°C). The invention also relates to an apparatus realising said method.

EFFECT: preventing precipitation of salts outside the reactor in order to prevent clogging of coiled pipes and simplification of the method.

2 cl, 1 dwg

Description

The invention relates to areas related to the use of hydrocarbons, namely, petrochemicals, oil refining, oil production, the chemical industry, where waste containing hydrocarbons is generated.

A known method of neutralizing waste containing hydrocarbons by burning at a thermal neutralization of liquid waste, including a cyclone furnace with tangentially arranged gas burners, nozzles for supplying liquid waste, a gas duct connected to an exhaust gas purification device, and a chimney (book "Fire processing and neutralization industrial waste ". M: Chemistry, 1990, p.206-208).

The disadvantages of this method are the need to use fuel, the irreversible loss of raw materials contained in the waste, and environmental damage to the environment.

There is a method of waste disposal by thermal disposal in an ozone-air environment (see RF Pat. No. 2289066, class C01 dated 03/10/2005, published on December 10, 2006, Bull. No. 34). The disadvantage of this method is the need to use fuel, an ozone generator and irreversible losses of raw materials contained in the waste.

A known method of wastewater treatment of petrochemical and oil refining industries from dissolved phenols and petroleum products by treatment with pulsed high-voltage discharges, followed by sedimentation. In order to increase the efficiency of purification from dissolved phenols and oil products, the wastewater is subjected to a combined treatment with high-voltage pulse discharges with a specific energy of 7-15 kJ / dm ³ followed by flotation, biological treatment and sorption on coal-sand filters (see US Pat. RF No. 96105609, CL C02F 1/48 dated 03/22/1996, publ. 06/10/1998).

The disadvantages of this method are its multi-stage and high energy costs.

A known method of disposal and subsequent disposal of highly viscous waste industrial wastewater with grass flour followed by treatment with carbonized grass flour (see US Pat. RF No. 2154617, CL C02F 11/14 from 09/28/1998, publ. 08/20/2000). The essence of the method is to absorb the hydrocarbon component of the waste structures of grassy flour, followed by the decomposition of hydrocarbons in the heat treatment process.

The disadvantages of this method are its multi-stage and a significant duration of the process.

A known method of disposal of the waste process of epoxidation of olefins by extraction with supercritical solvents (see US Pat. RF No. 2393152, CL C07D / B01J / C02F from 03.25.2008, publ. 09.27.2009).

The disadvantage of this method is the formation of a tail stream containing residual resins and macromolecular compounds.

Closest to the proposed one is a method of neutralizing waste products of tetrafthalic acid and liquid crystal displays by supercritical water neutralization with liquid hydrogen peroxide, including compressing the waste to a pressure of P> PcrH ₂ O, heating the waste to a temperature of T> TcrH ₂ O, compressing the oxidizer to a pressure of P> PcrH ₂ O, heating the oxidizing agent to a temperature T> TkrH ₂ O, feeding the waste and oxidizing agent to the reactor, followed by filtering the mixture through 0.5 micron filters and cooling in a heat exchanger (where RkrN ₂ O is critical water pressure - 218 atm, TkrN ₂ O - critical water temperature 374 ° C). After the heat exchanger, the mixture is fed to a separator, where there is a separation into liquid and gas phases. The method allows highly efficiently neutralize solvent waste to a safe state (Supercritical Water Oxidation of Industrial Wastewaters. Young Ho Shin, Banbang Veriansyah, Eun-Scok et al. 8 ^th International Symposium on Supercritical Fluids Kyoto (Japan), 2006).

The specified method is carried out using a device consisting of a pump for compressing waste, the output of which is connected to a heat exchanger for heating the waste, a pump for compressing the oxidizer, the output of which is connected to a heat exchanger for heating the oxidizer, heat exchangers for heating the waste and oxidizer, the outputs of which are combined and connected to the upper part a reactor, a one-way tubular reactor, the lower part connected to the filter unit, a filter unit consisting of two filters, alternating and connected to the refrigerator m, a refrigerator connected to the separator, separator.

The disadvantages of this method and device is the need for pre-heating the waste to a temperature T> TkrN ₂ O at a pressure P> PkrN ₂ O, which can lead to the precipitation of metal salts insoluble in supercritical water, and subsequent clogging of the coil (see Gazizov R.A. Workshop on the basics of supercritical fluid technologies / Gazizov R.A. and [others] - Kazan: Butlerovsky Heritage Innovation and Publishing House LLC, 2010. - 452 pp.), A filter unit requiring periodic cleaning is also used to trap salts and filtering replacements th element.

The objective of the invention is to prevent the precipitation of salts outside the reactor, simplifying the method while maintaining a high degree of neutralization.

The tasks are solved due to the fact that the method of neutralizing waste containing hydrocarbons, including compressing the waste and the oxidizing agent to a pressure of P> PcrH ₂ O with subsequent supply to the reactor, is carried out by oxidation in supercritical water at a temperature of T> TcrH ₂ O in the presence of an oxidizing agent while heating the waste to a temperature T> TkrN ₂ O produced recirculating supercritical solution neutralized waste directly in the reactor (wherein RkrN ₂ O - a critical pressure of water - 218 atm TkrN ₂ O - critical temp travel water 374 ° C).

The technical problem is also achieved by the fact that in the device for the disposal of waste containing a pump for waste, the outlet of which is connected to the upper part of the inner zone of the reactor, a pump or compressor for the oxidizer, the outlet of which is connected to ejectors located in the inner and outer zones of the reactor, has a two-way a tubular reactor equipped with a salt deposition zone with a filter screen, recycling devices for neutralized waste and sludge output, connected to the upper part of the outer zone with a separator waste through a pressure reducing device, the lower part with a precipitated sediment separator.

The use of air, oxygen enriched air, pure oxygen, alkali metals is proposed as an oxidizing agent. To compress air, it is proposed to use a compressor with a steam drive fed by a neutralized supercritical solution from the reactor. The use of high pressure pumps is proposed for dosing an alkali metal solution.

The method is as follows. Waste (initial waste) with a temperature T <TkrH ₂ O is pumped to the reactor. The waste is heated to a temperature T> TkrH ₂ O directly in the inner zone of the reactor due to hot recycle from the outer zone of the reactor. During the interaction of the initial waste and hot recycle, heat is redistributed, while the initial waste is heated to a temperature T> TkrN ₂ O, metal salts dissolved in the initial waste precipitate and precipitate in the lower part of the reactor, from where they are periodically removed from the reactor through the device sediment withdrawal. The oxidizer stream from the pump or compressor with a pressure exceeding the pressure of the Inner zone of the reactor is divided into two parts, the first oxidizer stream is supplied to the central part of the inner zone of the reactor, and hydrocarbons and partially metal salts decompose and oxidize to their oxides with increasing temperature of the mixture . The second oxidizing stream is fed to the lower part of the outer zone of the reactor, in which the oxidation of hydrocarbons occurs. The supply of both oxidizer streams is carried out through the ejector in order to create a pressure differential between the inner and outer zones of the reactor. The neutralized waste from the upper part of the outer zone of the reactor is divided into two streams, one stream, due to the pressure difference created by the ejectors, enters the inner zone of the reactor as a recycle through the recycled recycling device, and the second stream is removed from the reactor. The neutralized waste stream has a high kinetic energy and can be used in steam turbines (for example, for pumping air into the reactor if it is used as an oxidizing agent).

The quantitative distribution of the oxidizing agent between the streams depends on the requirements for the composition of the precipitate. If it is necessary to precipitate predominantly metal salts, the first stream can comprise from 25% to 50% of the total amount of oxidizing agent, if necessary, to obtain oxides in the precipitate, the first stream should contain from 50% to 75% of the total amount of oxidizing agent. The amount of hot recycle is controlled by temperature in the lower part of the inner zone of the reactor. The amount of oxidizing agent is controlled by the residual oxygen content at the outlet of the reactor, taking into account the value of COD (chemical oxygen demand).

The scheme of the device for waste neutralization is shown in Fig. 1, where 1 is the oxidizer pressure source, 2 is the waste pump, 3 is the reactor, which includes: 3.1 - the neutralized waste recirculation unit, 3.2 - the inner zone of the reactor, 3.3 - the salt deposition zone reactor, 3.4 - the outer zone of the reactor, 3.5 - site (device) output sediment, 3.6 - ejectors, 4,5 - separators.

The following examples describe the method of disposal of various wastes.

Example 1. As an initial waste, styrene and propylene oxide production waste is fed to the reactor at OAO Nizhnekamskneftekhim. Approximate waste composition:

- ethylbenzene C ₆ H ₅ CH ₂ CH ₃ - 2.5% wt .;

- acetophenone СН ₃ СОС ₆ Н ₅ - 1% wt .;

- methylphenylcarbinol (MPA) C ₆ H ₅ CH (OH) CH ₃ - 6.5% wt .;

- phenol C ₆ H ₅ OH - 2.5% wt .;

- propylene glycol C ₃ H ₈ O ₂ - 12% wt .;

- molybdenum Mo - 0.2% wt .;

- water N ₂ About - 40% wt. (according to the Fisher method);

- other - 35.3% wt.

The waste preheated to T <TkrH ₂ O is compressed by pump 2 to a pressure P> PkrH ₂ O and is fed into the inner zone of the reactor with a flow rate not exceeding 10% of the calculated value. As an oxidizing agent, air is used, compressed by a compressor with a steam-turbine drive (1 is marked in Fig. 1). To ignite the reactor 3, the oxidizer, preheated to T> TkrN ₂ O, is fed in one stream into the inner zone of the reactor 3.2. The mixture, having passed the internal 3.2 and external 3.4 zones of the reactor, is returned to the reactor in the form of a hot recycle through the recycled waste recycling unit 3.1. Upon reaching the operating temperature of the reactor T> TkrN ₂ O, the waste flow rate increases to the calculated one, the oxidizing agent is divided into two streams, the first stream, comprising 2/3 of the total amount, is fed into the inner zone of the reactor, the second stream, which is 1/3 of the total, into the outer zone of the reactor. To create a pressure drop inside the reactor and better mixture formation, the oxidant is fed through ejectors 3.6 located both in the inner and outer zones of the reactor. The neutralized waste at the outlet of the reactor is fed to the neutralized waste recycling unit 3.1, where it is divided into two streams, the first stream containing lighter components (mainly carbon dioxide and some water) is discharged from the reactor and fed to the steam compressor air turbine, from where it is supplied into the separator 5. A second stream containing heavier components (mainly water and a certain amount of carbon dioxide) is fed into the inner zone of the reactor 3.2 as a hot recycle. When the operating temperature is reached, the salts dissolved in the waste, in particular the molybdenum salts, are oxidized to higher oxides and precipitate in the salt deposition zone 3.3. From where, through the sediment withdrawal device 3.5, they are discharged to the sediment separator 5. To prevent salt entrainment by the upward waste stream, the space between the inner and outer zones of the reactor is blocked by a fine mesh (filter). In the sediment separator, by reducing the pressure, the residual water evaporates and dry sediment remains in the separator. To achieve a COD value of not more than 500 mgO ₂ / dm ^{3, the} temperature in the outer zone of the reactor should be 893 K, pressure 300 bar, waste: oxidizer ratio (21% O ₂ ) 1: 8, hot recycling: waste ratio 5: 1. The air supplied to the reactor contains a stoichiometric amount of oxygen. The recycle amount was selected taking into account the presence of phenol and other aromatic hydrocarbons, which form radicals at a concentration of more than 2% and do not completely oxidize (M.G. Gonikberg. Chemical equilibrium and reaction rate at high pressures. Khimiya Publishing House, Moscow, 1969 . - 428 p.).

Example 2 differs from example 1 in that oxygen (98%) is supplied as an oxidizing agent, and the waste: oxidizing agent ratio is 1: 1.5.

Example 3 differs from example 1 in that waste water from isoprene production is fed into the reactor as waste. Wastewater (CB) consists of three streams that are summed before being fed into the reactor:

CB-I stream - from the dimethyldioxane production unit - contains dissolved organic substances in an amount of over 110,000 mg / l; the chemical oxygen demand of the effluent is 283000 mgO ₂ / dm ³ ;

the CB-II stream — from the dimethyldioxane catalytic cleavage unit — contains about 3000 mg / L of dissolved organic matter; COD of runoff is 7400 mgO ₂ / dm ³ ;

CB-III flow from isoprene flushing unit. The amount of dissolved organic substances in this stream is about 400 mg / l, COD does not exceed 1000 mgO ₂ / dm. (Kovaleva N.G., Kovalev V.G. Biochemical wastewater treatment of chemical industry enterprises. - M .: Chemistry, 1987, 160 p.)

Upon reaching the operating temperature of the reactor T> TkrH ₂ O, the waste flow rate increases to the calculated one, the oxidizing agent is divided into two equal flows, the first stream is fed into the inner zone of the reactor, and the second stream into the outer zone of the reactor.

To achieve a COD value of not more than 500 mgO ₂ / dm ^{3, the} temperature in the outer zone of the reactor should be at least 850 K, pressure 300 bar, waste: oxidizer ratio (air 21% O ₂ ) 1: 7, hot recycling: waste ratio 1 :one.

Example 4 differs from example 1, 2 and 3 in that oil-oil emulsion formed in the sumps of treatment facilities of oil refineries is supplied as waste. This emulsion contains from 10 to 40% of petroleum products of various origin and dissolved metal salts.

Upon reaching the operating temperature of the reactor T> TkrN ₂ O, the waste flow rate increases to the calculated one, the oxidizing agent is divided into two streams, the first stream, comprising 2/3 of the total amount, is fed into the inner zone of the reactor, the second stream, which is 1/3 of the total, into the outer zone of the reactor.

To achieve a COD value of not more than 500 mgO ₂ / dm ^{3, the} temperature in the outer zone of the reactor should be at least 900 K, a pressure of 300 bar, a waste: oxidizer ratio of at least (air 21% O ₂ ) 1: 8, an expense ratio: hot recycling: waste 5: 1. Due to the inconsistency of the composition of this type of waste, the ratio of waste: oxidizer should be adjusted for the residual oxygen content in the neutralized waste, taking into account the COD value at the outlet.

Claims (2)

1. The method of neutralizing waste containing hydrocarbons, comprising compressing the waste and the oxidizing agent to a pressure of P> PcrH ₂ O followed by feeding to the reactor, is carried out by oxidation in supercritical water at a temperature of T> TcrH ₂ O in the presence of an oxidizing agent, characterized in that the heating waste to a temperature of T> TkrN ₂ O is produced by a recirculating supercritical solution of neutralized waste directly in the reactor (where RkrN ₂ O is the critical water pressure of 218 atm, TkrN ₂ O is the critical water temperature of 374 ° C). 2. A device for neutralizing waste containing a pump for waste, the outlet of which is connected to the upper part of the inner zone of the reactor, a pump or compressor for the oxidizer, the outlet of which is connected to ejectors located in the inner and outer zones of the reactor, characterized in that a two-way tubular reactor is used equipped with a salt deposition zone with a filter net, a neutralized waste recirculation unit and a sludge outlet connected to the upper part of the external zone with a neutralized waste separator through a reduction device Nia pressure lower part with separator deposited precipitate.