DESC:FIELD
The present disclosure relates to a process for on-site cleaning of an apparatus, particularly a refining/distillation column, a debutanizer column, and an olefin plant column with their exchangers, without dismantling the apparatus.
DEFINITIONS
As used in the present disclosure, the following words and phrases are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicate otherwise.
The expression “Popcorn polymer” for the purpose the present disclosure refers to a butadiene popcorn polymer. Popcorn polymer is the term given to the resinous, polymeric material which resembles popcorn in appearance and is dense, hard, non-extensible, and grows spontaneously in the presence of monomer.
The expression ‘Clinging’ for the purpose of the present disclosure refers to holding fast or adhering the popcorn polymers to the walls of the apparatus.

BACKGROUND
In the petrochemical industry, butadiene popcorn polymer formation is a major issue. The butadiene popcorn polymer is very sticky and difficult to remove. The reason of popcorn polymer formation is not well understood, but probably the conjugated dienes are responsible for the formation of the popcorn polymer.
Popcorn polymer is produced in the equipment when the concentration of butadiene is high (> 85%), specifically in the columns and exchangers of the equipment used in the butadiene plant. Further, the popcorn polymer is also formed in the equipment when low concentrations of olefins are present in the product fractionation segment. It is also observed that popcorn polymer does not need a seed of its own to grow, but it can grow on isoprene popcorn seeds and vice versa. Oxygen is the key element for the formation of the popcorn polymer; rust alone also has some ability to initiate the popcorn polymer formation in the absence of water.
The formation of popcorn polymer in the equipment/apparatus used in the butadiene plants usually creates a problem in cleaning, especially of the trays and the distillation/refining columns. The popcorn polymer also has a fouling issue. The growth of the popcorn polymer in the equipment cause pressure build up which can lead to rupture of pipes, condenser shells, valve bodies, and other metal parts of the equipment. Hence, the equipment needs to be kept clean, however the trays or distillation columns of the equipment cannot be cleaned on-site. The equipment has to be dismantled and mechanically cleaned off-site. The process of mechanical cleaning is tedious and time consuming.
Many researchers have reported various methods for the prevention/inhibition of popcorn polymer growth inside the apparatus. As the popcorn polymer is insoluble in many solvents, there is no solvent suggested in the art for complete removal of popcorn polymer from the apparatus.
Therefore, there is felt a need for a process for on-site cleaning of an apparatus having popcorn polymer present within the apparatus or clinging to the walls thereof, using a cleaning fluid.
OBJECTS
Some of the objects of the present disclosure which at least one embodiment herein satisfies, are as follows.
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative
An object of the present disclosure is to provide a process for on-site cleaning of an apparatus.
Yet another object of the present disclosure is to provide an environmentally friendly, simple, safe, and cost effective process for cleaning the apparatus.
Other objects and advantages of the present disclosure will be more apparent from the following description which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure provides a process for on-site cleaning of an apparatus having popcorn polymer within the apparatus or clinging to the walls thereof. The process involves a step of introducing a cleaning fluid into the apparatus, such as a refining/distillation column, a debutanizer column, and an olefin plant column with their exchangers. The cleaning fluid is tri-octyl ammonium chloride, which is allowed to remain or flow through the apparatus for a time period ranging from 6 hours to 12 hours under agitation and/or turbulence. The cleaning fluid solubilizes the popcorn polymer present in the apparatus. The cleaning fluid with dissolved popcorn polymer therein, is extracted from the apparatus and regenerated for further use. The apparatus can be cleaned without dismantling.
DETAILED DESCRIPTION
Conventionally used method for inhibiting the formation of the popcorn polymer in butadiene plants is not very effective and also, regrowth of the popcorn polymer is observed in the trays and distillation columns of the equipment used in butadiene plants. The equipment such as trays and distillation columns in the butadiene plants have to be dismantled and then cleaned mechanically. This process is difficult, laborious, time consuming, and requires skilled labors. Furthermore, this may roughen the tray surface which leads to popcorn formation in the next cycle. Thus, a huge production loss is incurred when using mechanical cleaning for the trays and distillation columns in the butadiene plants.
The inventors of the present disclosure envisaged a process for cleaning an apparatus having popcorn polymer therein. The process of the present disclosure solubilizes the popcorn polymer and is effective in on-site cleaning of the equipment used in the butadiene plants.
In accordance with the present disclosure, there is provided a process for on-site cleaning of an apparatus such as a refining/distillation column, a debutanizer column, and an olefin plant column with their exchangers. The process is described herein below.
A cleaning fluid is introduced into the apparatus having popcorn polymer within the apparatus or clinging to the walls thereof, in the petrochemical industry.
The cleaning fluid is tri-octyl ammonium chloride. The popcorn polymer can be one of conjugated diene, and is typically butadiene polymer.
In the present disclosure, tri-octyl ammonium chloride is prepared by adding concentrated HCl dropwise to tri-octyl amine in the temperature range of 20 oC to 40 °C to obtain a heterogeneous mixture containing an organic layer and an aqueous layer having pH 3.5. The reaction usually takes about 10 to 20 minutes to complete. The organic layer containing the fluid is separated from the aqueous layer to obtain the cleaning fluid. The so obtained cleaning fluid is tri-octyl ammonium chloride, which is characterized by NMR and IR spectra and compared with reported data. The tri-octyl ammonium chloride has the CAS No. 1188-95-0. The tri-octyl ammonium chloride is further dried under vacuum to obtain a solid which melts above 70 °C. The molar ratio of tri-octyl amine to conc. HCl used in the process of the present disclosure ranges from 1:1.1 to 1:1.2
The cleaning fluid, which is introduced into the apparatus, is allowed to stand in or flow through the apparatus for a time period ranging from 6 hours to 12 hours. The cleaning fluid is retained or flows through the apparatus under agitation and/or turbulence at a temperature in the range of 30 oC to 90 oC. The popcorn polymer present in the apparatus or adhered to the walls of the apparatus solubilizes in the cleaning fluid. The study of the effect of the amount of the cleaning fluid, time period, and different temperature used to solubilize the different amount of popcorn polymer are summarized in Table 2.
The cleaning fluid of the present disclosure solubilizes the popcorn polymer. Conventionally available solvent does not solubilize popcorn polymer. A list of the conventional solvents which were tested for solubilization of the popcorn polymer is summarized in Table-1.
It is observed that the popcorn polymer solubilizes in the fluid of the present disclosure, i.e. tri-octyl ammonium chloride, hence cleaning of the equipment used in the butadiene polymer plants becomes easy and effective. The process of dismantling the whole apparatus is not required and the production loss incurred for cleaning of the equipment is less. Cleaning of equipment using tri-octyl ammonium chloride requires 6-12 hours however conventionally used methods consumed almost 2-3 days for cleaning.
The tri-octyl ammonium chloride has comparatively better thermal stability and low vapor pressure. The boiling point of tri-octyl ammonium chloride is >360 °C at 760 mm Hg.
The cleaning fluid with dissolved popcorn polymer therein, is collected/ extracted from the apparatus after cleaning and is regenerated for further use.
The present disclosure is further described in the light of the following laboratory experiments which are set forth for illustration purpose only, and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale, and the results obtained can be extrapolated to industrial scale.

Experimental details:
Experiment 1: Preparation of cleaning fluid in accordance with the present disclosure-
The cleaning fluid, tri-octylammonium chloride was prepared by mixing 40 g of conc. HCl into 350 g of tri-octyl amine at 30 oC and at ambient pressure to obtain a heterogeneous mixture having a pH of 3.5. The so obtained heterogeneous mixture comprised an organic layer and an aqueous layer. The organic layer of was separated to obtain tri-octyl ammonium chloride fluid which is liquid at room temperature. The so obtained cleaning fluid was dried under vacuum to obtain a solid tri-octyl ammonium chloride.
Experiment 2: Solubility study of Popcorn polymer in various/conventional solvents-
Tests were carried out for studying solubility of the popcorn polymer in various solvents. In a round bottom flask, 1 g of popcorn type polymer (fouling material /sticky material) was placed. 10 g of different conventional solvents were added in the flask containing the popcorn polymer as given in table 1. The flask containing the popcorn polymer and the solvent, was stirred and heated up to the boiling point of the respective solvent for about 10-12 hours. The solubility of the popcorn polymer in each solvent is summarized in Table 1.
Table 1:
Sr. No. Solvent used Results
1 Benzene Neither swelling nor soluble
2 Toluene Neither swelling nor soluble
3 Cyclohexane Neither swelling nor soluble
4 Tetrahydrofuran Neither swelling nor soluble
5 Carbon tetrachloride Neither swelling nor soluble
6 Dichloromethane Neither swelling nor soluble
7 Dimethyl formamide Neither swelling nor soluble
8 Acetonitrile Neither swelling nor soluble
9 Dioxane Neither swelling nor soluble
10 Methanol Neither swelling nor soluble
11 DMSO-Dimethyl sulfoxide Neither swelling nor soluble
12 p-Xylene Neither swelling nor soluble
13 Dichlorobenzene Neither swelling nor soluble
14 Trichlorobenzene Neither swelling nor soluble
15 Dichloroethane Neither swelling nor soluble
16 Trichloroethane Neither swelling nor soluble
17 1,1,2,2-tetrachloroethane Noticeable swelling, but not soluble
18 Trichlorobenzene Neither swelling nor soluble
19 Mineral acids (HCl, H2SO4 etc) Neither swelling nor soluble
20 Aqua regia
(Aqua regia is a mixture of nitric acid and hydrochloric acid, optimally in a molar ratio of 1:3) Neither swelling nor soluble
21 10% NaOH Neither swelling nor soluble
22 Aliphatic & aromatic hydrocarbons of C9-C17 chain lengths Neither swelling nor soluble
23 Remax
(Remax is an aromatic solvent produced during the manufacture of xylenes. It consists of tetraethyl benzene and higher alkyl benzene). Neither swelling nor soluble

From table 1, it is evident that, the popcorn polymer is not soluble in any of the conventional solvent. Also, swelling of the popcorn polymer is not observed in any of the conventional solvent except 1,1,2,2- tetrachloroethane.
Experiment 3: Solubility of the popcorn polymer in tri-octyl amine-
In a 50 ml round bottom flask, 1 g of popcorn type polymer (fouling material /sticky material) was placed in 10 g of tri-octyl amine. The contents (popcorn polymer and the solvent) of the flask were stirred and heated up to the boiling point of tri-octyl amine (367 oC). The mixture was heated for 10-12 hours. Neither solubility nor swelling of the popcorn polymer was observed.
Experiment 4: Solubility of popcorn polymer in the cleaning fluid of the present disclosure-
0.1780 g of the popcorn polymer (fouling material) was taken in a round bottom flask and 10.6028 g of tri-octylammonium chloride (cleaning fluid) was added to it. The popcorn polymer and tri-octylammonium chloride mixture was heated at 50oC with stirring for 12 hours. A high level of swelling and disintegration was observed in tri-octylammonium chloride ((Octyl)3NHCl) after 10-11 hrs (refer experiment no. 7 of table 2).
In another flask 0.5312 g of the popcorn polymer (fouling material) was taken and 10.6068 g of tri-octylammonium chloride (cleaning fluid) was added to the flask. The mixture of popcorn polymer and tri-octylammonium chloride was stirred and heated up to 50oC for 12 hours. Low swelling and disintegration was observed as compared to 0.1780 g of popcorn polymer (fouling material) in tri-octylammonium chloride after 10-11 hours.
Similar experiments were conducted at elevated temperatures such as 70 oC, 90 oC and above. The fouling material (Popcorn polymer) disintegrated in tri-octylammonium chloride after 4-5 hours at 70 oC and 3-4 hours at 90 oC.
However, on cooling this reaction mixture to room temperature the reaction mixture containing tri-octylammonium chloride became a solid. Complete solubility was noticed in 7-12 hours when the popcorn polymer in tri-octylammonium chloride was heated above 100 oC.
The effect of time, temperature, and amount of the cleaning fluid used to solubilize the different amounts of popcorn polymer are summarized in Table 2.

Table 2:
Expt. No Cleaning fluid Amount of cleaning fluid (g) Amount of polymer (g) Temperature (0C) Time
(hours) Observations
1 (Octyl)3NHCl 10.6028 0.1780 50 7 hr High amount of visible swelling.
2 (Octyl)3NHCl 10.6069 0.5312 50 7 hr Visible swelling.
3 (Octyl)3NHCl 10.6068 0.5312 70 7 hr Visible swelling and disintegration.
4 (Octyl)3NHCl 10.6028 0.1780 70 7 hr High amount of visible swelling and crumbling.
5 (Octyl)3NHCl 10.580 0.5412 90 7 hr Visible swelling and crumbling.
6 (Octyl)3NHCl 10.597 0.1773 90 7 hr High amount of visible swelling and crumbling.
7 (Octyl)3NHCl 10.6028 0.1780 50 12 hr High amount of visible swelling and disintegration.
8 (Octyl)3NHCl 10.6069 0.5312 50 12 hr High amount of swelling.
9 (Octyl)3NHCl 10.6068 0.5312 70 12 hr Visible swelling and high disintegration.
10 (Octyl)3NHCl 10.6028 0.1780 70 12 hr High amount of visible swelling and appreciable crumbling.
11 (Octyl)3NHCl 10.580 0.5412 90 12 hr Visible swelling and partially popcorn polymer get solubilized.
12 (Octyl)3NHCl 10.597 0.1773 90 12 hr Popcorn polymer gets solubilized.

Table 2 reveals that, the popcorn polymer has significant swelling and disintegration in (Octyl)3NHCl (tri-octyl ammonium chloride), however, when the popcorn polymer (fouling material) was heated at elevated temperature (70 oC to 90 oC) for 12 hours or more, it solubilizes. Moreover, the ratio of solvent to popcorn polymer also affects the solubility. Higher the amount of popcorn polymer in solvent, lower is the swelling, disintegration and solubility of the popcorn polymer.
Experiment 5: On-site cleaning of apparatus using tri-octylammonium chloride in accordance with the process of the present disclosure
Tri-octylammonium chloride can be used in cleaning the columns containing fouling materials. To study the efficiency of tri-octylammonium chloride for cleaning the columns containing fouling materials, pilot scale trials and experiments were carried out on-site.
The column was heated to 50 oC using hot air. The amount of tri-octylammonium chloride taken for the cleaning the column was 10 % of the volume of the column. Tri-octylammonium chloride was preheated to 50 oC and then passed into the column at the rate of 50 mL/min. The direction of the flow was such that tri-octylammonium chloride flows through all the surfaces of the column. Tri-octylammonium chloride was recirculated repeatedly over a period of 12 hours. Care was taken to incorporate a filter unit at the exit point of the column so that particles do not enter into the flow system. After 12 hours, tri-octylammonium chloride was removed and the column was cleaned with hydrojets which were able to dislodge the popcorn polymer easily.
Therefore, it can be concluded from experiments 1-5 that the popcorn type polymer (butadiene polymer) is cross linked polymers as shown by non-swelling and non–solubilization properties in standard solvents. Since butadiene polymer is formed in the butadiene column and it is well known that it is not cross linked, it is expected that there is some material that helps to cross- link the butadiene polymer. Further analysis has shown that the butadiene polymer contains iron. So it is anticipated that the iron may be involved in the cross linking of butadiene polymer. Tri-octylammonium chloride used in the present disclosure is a quaternary salt formed from tri-octyl amine which can be used for iron recovery. Tri-octylammonium chloride forms a complex and leaches out iron and thus degrades the insoluble polymer for easy solubilization and removal, as compared to the conventional solvents.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a process that:
? facilitates solubilization of the popcorn polymer;
? can be used for effective cleaning of equipment in a short time period;
? provides comparatively higher stability of the cleaning fluid;
? enables regeneration of the cleaning fluid for further use;
? aids closed-loop operation, with no need to open units during cleaning of equipment;
? is safe and environmentally friendly operation; and
? leads to no waste generation and no emissions.
The foregoing description of the specific embodiments so fully reveals the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
,CLAIMS:1. A process for on-site cleaning of an apparatus, such as a refining/distillation column, a debutanizer column, and an olefin plant column with their exchangers, without dismantling the apparatus, said apparatus having popcorn polymer within the apparatus or clinging to the walls thereof, said process comprising the following steps:
a. introducing a cleaning fluid into the apparatus;
b. allowing said cleaning fluid to remain or flow through the apparatus for a time period ranging from 6 hours to 12 hours; and
c. extracting, from said apparatus, said cleaning fluid with dissolved popcorn polymer therein.

2. The process as claimed in claim 1, wherein said cleaning fluid is retained or flows through the apparatus under agitation and/or turbulence.

3. The process as claimed in claim 1, wherein said cleaning fluid contains tri-octyl ammonium chloride.

4. The process as claimed in claim 1, wherein said popcorn polymer is one of conjugated diene, typically butadiene polymer.

5. The process as claimed in claim 3, wherein said tri-octyl ammonium chloride is obtained by reacting tri-octyl amine with HCl.