JP2832493B2 - Cleaning of equipment used for liquid phase oxidation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to the cleaning of equipment used in liquid oxidation processes. In the description and in the claims, the term "liquid-phase oxidation process" refers to the term "liquid-phase oxidation", which refers to the reaction of an aqueous solution of a reactant containing iron (III) and an organic acid with a coordination complex with the melting point of sulfur in the contact zone. Increased concentrations of solubilized coordination complex of iron (II) and organic acids containing treated gas with reduced hydrogen sulfide content and solid sulfur upon contact under conditions to convert hydrogen sulfide at lower temperatures Used to refer to a method of removing hydrogen sulfide from a gas that produces an aqueous mixture. In another zone, sulfur is removed from the aqueous mixture and iron (II) is oxidized to iron (III) to regenerate the aqueous mixture used in the contact zone.

[0002] The equipment used in the above process is elemental sulfur produced in the contact zone; iron sulfide and iron hydroxide produced by the reaction of the reactant iron with an excess of hydrogen sulfide; and carryover as mist from upstream processing of the gas. Exposed to fouling caused by the deposition of heavy hydrocarbons. It is known to use aqueous reactants to remove mechanically loose elemental sulfur and to use surfactants to control oil film formation. It is an object of the present invention to provide a composition for cleaning equipment used in a liquid phase oxidation process which can effectively control the above three types of soil. For this purpose, the composition for cleaning the equipment used in the liquid phase oxidation process according to the invention comprises 3 to 30% by weight of sulfite salt, 0.5 to 30% by weight of chelating agent.
And a 0.05 to 5% by weight aqueous solution of a cationic surfactant.

[0003] The salt of sulfite can be sulfite or bisulfite. Sulfite (or bisulfite) will form thiosulfate, soluble in elemental sulfur and water. Inactive iron sulfide and iron hydroxide are dissolved by the chelating agent which forms the molecular structure to which the iron ions are bound. Cationic surfactants will facilitate oil removal. However, cationic surfactants also have a beneficial effect on the reaction of sulfites (or bisulfites) with sulfur to thiosulfates and on the dissolution of iron hydroxide. An advantage of the present invention is that the cleaning composition containing dissolved contaminants contains harmless substances that are compatible with the aqueous reactant solution. Suitably the sulfite salt is an ammonium or sodium salt.

[0004] The chelating agent can be a salt such as an organic acid or the ammonium or sodium salt of an organic acid. The organic acid is suitably nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA) or hydroxyethylenediaminetetraacetic acid (HOEDTA).
Nitrogen polyacid). Suitably, the cation in the sulfite salt is the same as the cation associated with the chelating agent. Further, the chelating agent of the cleaning composition is suitably the same as the chelating agent used in the liquid phase oxidation process.

The cationic surfactant is suitably a quaternary ammonium salt, for example a dialkyldimethylammonium salt, an alkylbenzyldimethylammonium halide such as an alkylbenzyldimethylammonium halide, an alkyltrimethylammonium salt or an alkylpyridinium halide such as dodecylpyridinium bromide. is there.

The contact of the composition according to the invention with the soiled equipment is carried out at a temperature of from 10 to 80 ° C. The present invention will be described in more detail by way of example with reference to the accompanying drawings. In the figure, the broken line shows the conduit used in the liquid phase oxidation method, and the solid line shows the conduit used when cleaning the apparatus used in the liquid phase oxidation method.

The gas from which hydrogen sulfide is to be removed is supplied at elevated pressure to the co-current contactor 6 via conduit 4 and the aqueous reactant is supplied to the co-current contactor 6 via conduit 8. The reactant solution contains a solubilized coordination complex of iron (III) and NTA. The gas and reactant solution are contacted in a contactor 6 under conditions to convert hydrogen sulfide to elemental sulfur, a treated gas having a reduced hydrogen sulfide content, and solid sulfur and an increased concentration of iron (II) And an aqueous mixture comprising a solubilized coordination complex of NTA and NTA. The gas / liquid mixture is passed from the co-current contactor 6 through conduit 9 to a gas-liquid separator 10.
The gas processed therefrom passes through conduit 12 and passes through solid sulfur and increased concentrations of iron (II) and NT.
The aqueous mixture containing the solubilized coordination complex of A is withdrawn through conduit 15.

The aqueous mixture passes through conduit 15 through oxidizer 19
The iron (II) reduced therein is oxidized to iron (III) by air supplied to the lower part of the oxidizer 19 through a conduit 24 by a blower 23. The conditions for oxidizing the reduced reactants are irrelevant to the present invention. The regenerated reactant is withdrawn from oxidizer 19 through conduit 26 and fed to co-current contactor 6 through conduit 8 by circulation pump 27. A sulfur-rich slurry is withdrawn from the bottom of the oxidizer 19 through a conduit 30 and the solution is pumped 3
1 to further treat the sulfur and feed it to means for storing the sulfur (not shown). The depleted air leaves the top of the oxidizer 19 through conduit 35.

To clean the equipment used in the above process, the process is interrupted, the contactors are depressurized and the cleaning composition is removed from tank 36 by circulating pump 27 to conduit 3.
Through 7 and 38 to the co-current contactor 6 and from there back to the tank 36 via conduit 42. The cleaning composition used comprises 10% by weight of ammonium sulfite, 10% by weight of ammonium NTA and 0.1% by weight of dodecylpyridinium bromide. The cleaning composition is provided in conduit 38
It is heated to a temperature of 60 ° C. by the heat exchanger 43 inside. When the washing is completed, the composition is drained into a tank and a clean co-current contactor 6 is put into use.

[0010] For clarity, the conduit system for passing the cleaning composition is shown separately from the conduit system for passing the aqueous reactant solution. However, it will be understood that the conduit system for passing the aqueous solution of reactants during normal operation is included in the conduit system for passing the composition. In this way, a part of the conduit system is cleaned in addition to the circulation pump 27. Suitably the plant includes two co-current contactors with their associated circulation pumps, whereby there are co-current contactors that can take over service from the contactor being cleaned.

[Brief description of the drawings]

FIG. 1 is a diagram showing the configuration of a plant for a liquid phase oxidation method involving regeneration of an aqueous reactant.

[Explanation of symbols]

 6 Co-current contactor 10 Gas-liquid separator 19 Oxidizer 36 Cleaning composition tank

────────────────────────────────────────────────── (5) References JP-A-54-71787 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C11D 10/02 C11D 1/62 C11D 7 / 10 C11D 3/30

Claims (6)

(57) [Claims] An apparatus for use in a liquid phase oxidation method comprising an aqueous solution of 3 to 30% by weight of a sulfite salt, 0.5 to 30% by weight of a chelating agent and 0.05 to 5% by weight of a cationic surfactant. Cleaning composition. 2. The composition of claim 1 wherein the sulfite salt is an ammonium salt or a sodium salt. 3. The composition according to claim 1, wherein the chelating agent is an organic acid. 4. The composition according to claim 3, wherein the chelating agent is an ammonium salt of an organic acid. 5. The composition according to claim 3, wherein the organic acid is nitrilotriacetic acid or ethylenediaminetetraacetic acid. 6. The composition according to claim 1, wherein the cationic surfactant is a quaternary ammonium salt.