FORM-2
THE PATENTS ACT
(39 OF 1970)
AND
THE PATENT RULES,2003
(AS AMENDED)
COMPLETE SPECIFICATION (SEE SECTION 10; RULE 13)
PROCESS FOR IMPROVING THERMAL STABILITY AND WATER SEPARATION CHARACTERISTIC OF ATF TYPE PETROLEUM DISTILLATE
NAYARA ENERGY LIMITED, a corporation organized and existing under the laws of India, 39 KM Jamnagar-Okha Highway, Vadinar, Dist Devbhoomi Dwarka, Gujarat,
India.
The following specification particularly describes the invention and the manner in which it is to be performed:
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The present invention is a patent of addition of Indian application no. 202221041847, dated 21.07.2022 entitled “Process for improving quality of kerosene type petroleum distillates by adsorbent technique”.
Title of Invention:
Process for improving thermal stability and water separation characteristic of aviation turbine fuel (ATF) type petroleum distillates.
Field of the invention:
The present invention relates to crude oil refining process, more specifically to improve thermal stability and water separation characteristic of aviation turbine fuel type petroleum distillates that produced from crude oil by adsorbent technique, furthermore specific to petroleum product namely, aviation turbine fuel (Turbine Fuel, Kerosene Type, Jet A- 1; NATO Code: F-35; Joint Service Designation: AVTUR, Jet Fuel etc), mineral turpentine oil, superior kerosene oil, petroleum hydrocarbon solvent etc.
Background of the invention:
Crude oil is fossil fuel extracted from earth, sometime synthetic material also mixed with it. After exploration and cleaning process, crude oil mainly consists of mixture of hydrocarbon and trace quantity of water and sediments. Petroleum refiners process different types of crude oils and produce valuable gaseous and liquid fuels namely Liquefied Petroleum Gas (LPG), Motor Spirit (MS), Aviation Turbine Fuel (ATF), Superior Kerosene Oil (SKO), Mineral Turpentine Oil (MTO), Diesel, etc. and solid products like Sulphur and Petroleum Coke. The kerosene fraction of distillates are mainly used to produce ATF, MTO, SKO and petroleum hydrocarbon solvents.
The aviation turbine fuel can be a blend of non-hydroprocessed kerosene, hydroprocessed kerosene and synthetic kerosene components.
The non hydro processed kerosene is produced through sweetening process called MERICHEM or MEROX treatment to remove impurities namely hydrogen sulphide, mercaptans, naphthenic acids and surfactants etc. The hydro processed kerosene is produced using hydro treatment. Also, kerosene produced from vacuum gas oil mild hydro cracking is being blended to produce aviation turbine fuel.
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The aviation turbine fuel (ATF) is being used as fuel for aircraft, it is also additionally used as coolant to remove waste heat loads in the modern aircraft. The aviation turbine fuel is being tested as per standard product specifications viz IS-1571 or Defence Standard 91-091. There are various critical quality parameters are defined in standard specification of ATF to take care of engine performance as well as safety of aircraft fuel system components. The thermal stability and water separation characteristic of ATF are among a very important parameter. As the fuel temperature increases, several reactions involving hydrocarbon molecules, dissolve oxygen, and impurities take place, which ultimately leads to the formation of gums and solid deposits. The gum formation can constrict the fuel flow, potentially cause as engine shutdown, and decrease the heat exchange efficiency. Hence ATF must be thermally stable and has to meet the thermal stability requirement specified in the standard specifications.
The presence of free water in ATF can get freeze within an aircraft fuelling system which can lead to serious damage hence free water must be removed from fuel. Generally, filter separator system (coalescing type filter) is being used to remove free water from ATF. The small amount of surface-active material (also known as surface active agent or surfactants) affect the ability of filter separators to separate free water from fuel. Hence ATF must be free from surface active materials and meet the water separation characteristics mentioned in the standard specifications.
The requirements of thermal stability and water separation characteristics specified in the standard specifications DEF STAN 91-091, Issue 14 & IS 1571, 2018 are mentioned in below table 1.
Table 1: Requirements of thermal oxidation stability and water separation characteristics

Sr. No. Test Method Properties UOM Limits
1 ASTM D 3241, IP 323, IS 1448 Part 97 Thermal Stability by Jet Fuel Thermal Oxidation Tester (JFTOT) at 260 Deg. C - -

By Visual Tube Rating - Less than 3, No peacock (P) or Abnormal (A)

By Interferometric (ITR) Or Ellipsometric (ETR) method Nano
meter,
Maximum 85
3

Pressure Difference Mm Hg, Maximum 25
2 ASTM D 3948, IS 1448 Part 142 Water Separation by Micro-separometer at point of manufacture. - -

MSEP Without SDA Rating, Minimum 85

MSEP With SDA Rating, Minimum 70
Even though, petroleum refinery is having standard manufacturing facility to produce ATF, sometime fuel found to be failed in thermal stability or in water separation characteristic due to dynamic feed processing which leads to down gradation of product. The attapulgite clay treatment is being used to remove surfactant which help to meet the water separation characteristic. The antioxidant additive is being added to the aviation turbine fuel produced from vacuum gas oil mild hydro cracker (VGO-MHC) to improve fuel storage stability which is not effective in improving thermal stability and there is no direct control of thermal stability in the existing VGO-MHC process, ultimately it restrict the blending of VGO-MHC kerosene cut into ATF pool, hence refiner strive for reliable process to improve and control the thermal stability of ATF.
In these cases, product is downgraded or has to be used for other less valuable applications, which ultimately reduces profit margin of the refiner.
There is very limited literature available on methods to improve thermal stability and water separation characteristic of aviation turbine fuel. PCT publication number WO 2011/068663 A1 relates to increasing colour quality and thermal stability of fuel by treating with an acidic ion exchange resin. US patent No. 3,487,012 relates to a process for the improvement of initial colour and long-term stability of aromatic concentrates boiling between 400 to 750 deg. F by process comprises hydrotreating, acid treating followed by caustic washing, and vacuum distillation.
The thermal stability and water separation characteristic of aviation turbine fuel product is purely depends on chemical composition of crude oil and refining process & technology used for production. Generally, Merichem or Merox sweetening process used for straight run ATF and not for hydrotreated ATF, where attapulgite clay bed provided to improve
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water separation characteristic. There are some drawbacks of attapulgite clay, it is natural product hence quality changed geographically as well as time to time, availability problems in rainy season, become muddy while absorb water hence it is difficult to unload from bed. As of today, there is no easy, efficient, and economical process well known to the refining fraternity for production of ATF from straight run or VGO-MHC kerosene with desired thermal stability and water separation characteristics.
Looking to the above problems, crude oil refiners are striving to improve thermal stability and water separation characteristics of VGO-MHC kerosene by easy, efficient, and economical process. Therefore, it would be of great benefit to the refining fraternity if easy, efficient, and economical process is made available for them for said purpose. Hence, need arises to develop easy, efficient, and economical process to improve thermal stability and water separation characteristic of aviation turbine fuel type petroleum distillates, which are going between 50 to 380 ℃.
Object of the Invention:
The main object of present invention is to improve quality of aviation turbine fuel type petroleum distillates.
Further, object of the present invention is to provide a process to improve quality of aviation turbine fuel type petroleum distillates by adsorbent technique.
Yet another object of present invention is to develop a process to improve thermal stability and water separation characteristic of aviation turbine fuel type petroleum distillates.
Yet another object of present invention is to improve quality of aviation turbine fuel type petroleum distillate with respect to thermal stability, water separation characteristic, Saybolt color, improve stability of Saybolt color, organic nitrogen content, moisture content.
Another object of present invention is to develop a process to improve thermal stability and water separation characteristic of aviation turbine fuel type petroleum distillates and regeneration of adsorbent.
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Another object of present invention is to improve thermal stability and water separation characteristic and regenerate the used adsorbent of aviation turbine fuel type petroleum distillates.
Yet another objective of the present invention is to develop a process to improve thermal stability and water separation characteristic of aviation turbine fuel type petroleum distillates having distillation range between 125 to 300°C or beyond of this range.
Yet another objective of the present invention is to develop a process to improve thermal stability and water separation characteristic of aviation turbine fuel type petroleum distillates using batch or continuous process.
Yet another objective of the present invention is to develop a process to improve thermal stability and water separation characteristic of aviation turbine fuel type petroleum distillates using ambient or any temperature.
Yet another objective of the present invention is to develop a process to improve thermal stability and water separation characteristic of aviation turbine fuel type petroleum distillates using ambient or any other pressure.
Yet another objective of the present invention is to develop a process to improve thermal stability and water separation characteristic of aviation turbine fuel type petroleum distillates using different suitable flow rate.
Yet another objective of the present invention is to develop a process to improve thermal stability and water separation characteristic of aviation turbine fuel type petroleum distillates using single or multiple types of adsorbents.
Yet another objective of the present invention is to develop a process to improve thermal stability and water separation characteristic of aviation turbine fuel type petroleum distillates using single or multiple adsorbent beds.
Yet another objective of the present invention is to develop a process to improve thermal stability and water separation characteristic of aviation turbine fuel type petroleum distillates using any suitable particle size, shape and color of silica gel adsorbent.
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Yet another objective of the present invention is to develop simple process to improve thermal stability and water separation characteristic of aviation turbine fuel type petroleum distillates.
Yet another objective of the present invention is to develop a cost-effective process to improve thermal stability and water separation characteristic of aviation turbine fuel type petroleum distillates.
Yet another objective of the present invention is to develop simple and cost-effective process to improve thermal stability and water separation characteristic of aviation turbine fuel type petroleum distillates.
Yet another objective of the present invention is to recover hydrocarbon from used adsorbent.
Yet another objective of the present invention is to reduce hydrocarbon hazard from used adsorbent.
Yet another objective of the present invention is to reduce fire hazard from used silica gel thus will improve operation safety.
Yet another objective of the present invention is to develop regeneration process for used adsorbent for reuse.
Yet another objective of the present invention is to develop regeneration process for used adsorbent at 500 to 1000°C and beyond this temperature range.
Yet another objective of the present invention is to develop regeneration process for used adsorbent with initially nitrogen or inert gas purging.
Yet another objective of the present invention is to develop regeneration process for used adsorbent with air purging.
Yet another objective of the present invention is to develop regeneration process for used adsorbent with hydrocarbon recovery.
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Yet another objective of the present invention is to develop regeneration process using batch or continuous process.
Yet another objective of the present invention is to reduce volatile organic carbon hazards thus reduce air pollution.
Yet another objective of the present invention is to develop procedure to measure adsorbent thermal stability improvement efficiency.
Yet another object of present invention is to develop an alternate adsorbent in place of attapulgite clay used for ATF production.
Yet another object of present invention is to use of adsorbent which produced synthetically to get consistent quality.
Yet another object of present invention is to develop an adsorbent which can be used in blend with attapulgite clay used for ATF production.
Yet another object of present invention is to develop an adsorbent which not generating mudding while absorb water.
Yet another object of present invention is to develop an adsorbent which can easily unloaded from adsorbent bed compared to attapulgite clay.
Improvement over main application
The Applicant has earlier invented process for improving quality of kerosene type petroleum distillates by adsorbent technique and Indian patent application number 202221041847 is filed on dated 21.07.2022. In said main patent application, it was claimed that the invented silica gel adsorbent process is improving quality parameters namely saybolt colour, stability of saybolt colour and it is reducing organic nitrogen and water content. Further research work was carried out with respect to improvements of thermal stability and water separation characteristic, which are very important quality parameters of aviation turbine fuel.
Summary of the Invention:
In order to achieve the afore-said objectives, present invention provides a novel process to improve thermal stability and water separation characteristic of aviation turbine fuel
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type petroleum distillates, and process to recover hydrocarbon and regeneration of used adsorbent.
As per the first aspect the process of the present invention is a simple three step process comprising following steps:-Step-1: passing the aviation turbine fuel type petroleum distillate through silica gel adsorbent bed to improve the thermal stability and water separation characteristic; Step-2: recovering surface hydrocarbon from used silica gel by water washing; or recovering surface and adsorbed hydrocarbon by thermal regeneration; Step-3: regenerating used silica gel by thermal oxidation.
In one of the embodiment the present invention further provides the process for treating
aviation turbine fuel type petroleum distillate comprising:
Step-1: passing aviation turbine fuel type petroleum distillate through silica gel;
Step-2: recovering surface hydrocarbon from used silica gel by water washing;
Step-3: regenerating used silica gel obtained after Step-1 or after Step-2 by thermal
oxidation.
In another embodiment the present invention provides a process for thermal oxidation
comprises:
Step-1: raising furnace temperature from ambient to 350°C at the rate of 100°C per hour
while purging nitrogen;
Step-2: switching purging gas from nitrogen to air and raising furnace temperature up to
700 °C.
In another embodiment the present invention provides a process for treating ATF type petroleum distillate, wherein the efficiency of thermal stability improvement is ~ 99000 nanometers per ml of sample per gm of silica gel.
In yet another embodiment of present invention, the wherein the silica gel is blended with other adsorbents like attapulgite clay.
In another embodiment the present invention provides a process for treating ATF using silica gel with attapulgite clay, wherein the quality of ATF improves.
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In another embodiment the present invention provides a process for preparing adsorbent bed using silica gel with attapulgite clay, wherein the chance of mud generation at bottom of adsorbent bed is reduce.
In another embodiment the present invention provides a process for preparing adsorbent bed using silica gel with attapulgite clay, wherein the unloading of adsorbent bed is easy.
In another embodiment the present invention provides the process for treating ATF type petroleum distillate, wherein the process improves thermal stability, water separation characteristic, Saybolt color and stability of saybolt colour as well as process reduce nitrogen content and water content of ATF, recovers hydrocarbon from used silica gel and regenerates used silica gel.
In another embodiment the present invention provides the process for treating ATF type petroleum distillate, wherein the treated ATF is meeting all the standard product specification parameters and there is no significant adverse impact on any parameters.
Description of the Drawings:
The foregoing and further objects, features and advantages of the present subject matter will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements.
It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter, and are therefore, not to be considered for limiting of its scope, for the subject matter may admit to other equally effective embodiments.
Figure 1: Illustrates the basic silica gel adsorbent process to improve the thermal
stability and water separation characteristic of ATF type petroleum distillates.
Figure 2: Illustrates the basic process for recovery of surface hydrocarbon from used
silica gel by water washing.
Figure 3: Illustrates the basic process for regeneration of used adsorbent with
hydrocarbon recovery.
Figure 4: Image of white silica gel crystal used as adsorbent.
Figure 5: Image of lab scale 300 ml adsorbent bed for experiment.
Figure 6: Image of ATF sample before and after silica gel treatment.
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Figure 7: Image of pilot skid for adsorbent treatment.
Figure 8: Image of used silica gel.
Figure 9: Image of lab scale water washing system to recover surface hydrocarbon from
used silica gel.
Figure 10: Image of lab scale silica gel thermal regeneration system.
Figure 11: Image of recovered hydrocarbon from water washing and thermal
regeneration system.
Figure 12: Image of regenerated silica gel.
Figure 13: Images of fresh, used and regenerated silica gel.
Figure 14: Images of Thermal Stability Analyser (Jet Fuel Thermal Oxidation Tester -
JFTOT) instrument comply with the requirements of standard test methods viz. ASTM D
3241, IP 323 and IS 1448 Part 97 and make by M/s Expoteck USA, INC, Model -FALEX
400.
Figure 15: Images of automated deposit rater comply with the requirements of standard
test methods viz. ASTM D 3241, IP 323 and IS 1448 Part 97 . The automated
interferometry technique (ITR) makes by M/s AD Systems Model- DR 10 was used for
deposit thickness measurement.
Figure 16: Images of Micro-Separometer instrument comply with the requirements of
standard test- methods viz. ASTM D 3948 and IS 1448, Part 142 and makes by M/s
EMCEE Electronic INC, USA, Model 1140 Micro-separometer, Mark X.
Figure 17: Image of deposit on fresh heater tube [A], heater tube after passing of dirty
ATF sample [B] and heater tube after passing of silica gel treated ATF sample [C].
Detailed description of the invention:
The following presents a detailed description of various embodiments of the present subject matter with reference to the accompanying drawings.
The embodiments of the present subject matter are described in detail with reference to the accompanying drawings. However, the present subject matter is not limited to these embodiments which are only provided to explain more clearly the present subject matter to a person skilled in the art of the present disclosure. In the accompanying drawings, like reference numerals are used to indicate like components.
The specification may refer to “an”, “one”, “different” or “some” embodiment(s) in several locations. This does not necessarily imply that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.
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As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes”, “comprises”, “including” and/or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being “attached” or “connected” or “coupled” or “mounted” to another element, it can be directly attached or connected or coupled to the other element or intervening elements may be present. As used herein, the term “and/or” includes any and all combinations and arrangements of one or more of the associated listed items.
The figures depict a simplified structure only showing some elements and functional entities, all being logical units whose implementation may differ from what is shown.
The present invention provides a novel process to improve thermal stability and water separation characteristic of ATF type petroleum distillates, and process to recover hydrocarbon and regeneration of used adsorbent.
The process of the present invention is a simple three step process comprising following steps:-Step-1: passing the ATF type petroleum distillate through silica gel adsorbent bed to improve the thermal stability and water separation characteristic;
Step-2: recovering surface hydrocarbon from used silica gel by water washing; or recovering surface and adsorbed hydrocarbon by thermal regeneration; Step-3: regenerating used silica gel by thermal oxidation.
In one of the embodiment the present invention further provides the process for treating
ATF type petroleum distillate comprising:
Step-1: passing ATF type petroleum distillate through silica gel;
Step-2: recovering surface hydrocarbon from used silica gel by water washing;
Step-3: regenerating used silica gel obtained after Step-1 or after Step-2 by thermal
oxidation.
In another embodiment the present invention provides a process for thermal oxidation comprises:
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Step-1: raising furnace temperature from ambient to 350°C at the rate of 100°C per hour
while purging nitrogen;
Step-2: switching purging gas from nitrogen to air and raising furnace temperature up to
700 °C.
In another embodiment the present invention provides a process for treating ATF type
petroleum distillate, wherein the efficiency of thermal stability improvement is ~ 99000
nanometers per ml of sample per gm of silica gel.
In another embodiment the present invention provides a process for treating ATF using silica gel with attapulgite clay, wherein the quality of ATF improves.
In another embodiment the present invention provides a process for preparing adsorbent bed using silica gel with attapulgite clay, wherein the chance of mud generation at bottom of adsorbent bed is reduce.
In another embodiment the present invention provides a process for preparing adsorbent bed using silica gel with attapulgite clay, wherein the unloading of adsorbent bed is easy.
In another embodiment the present invention provides the process for treating ATF type petroleum distillate, wherein the process improves thermal stability, water separation characteristic, Saybolt color and stability of saybolt colour as well as process reduce nitrogen content and water content of ATF, recovers hydrocarbon from used silica gel and regenerates used silica gel.
In another embodiment the present invention provides the process for treating ATF type petroleum distillate, wherein the treated ATF is meeting all the standard product specification parameters and there is no significant adverse impact on any parameters.
The present process provides improved thermal stability, improved water separation characteristic of ATF type petroleum distillates, recovery of hydrocarbon and regeneration of adsorbent. The invented process is verified at laboratory scale. The detailed description of process is as mentioned below.
Step-1 Process to Improve Saybolt Color:
As per Figure 1, the ATF type petroleum distillate [1] that is produced at crude oil refinery is feed to the silica gel adsorbent bed [2] via valve [V1] and improved ATF type distillate product is collected from outlet line [3] via valve [V2]. The process can be operated at
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ambient temperature and pressure, or these parameters can be adjusted as per requirements. The process can be also used with single (silica gel) or mixture with other adsorbent (attapulgite clay etc). The process can be also operated at single or multiple adsorbent beds based on requirements. The flow can be passed from top to bottom or from bottom to top. The experiments conducted at laboratory scale indicate that the present process is capable to improve thermal stability, improve water separation characteristic as mentioned in experimental study work. After exhaustion of adsorbent life, close the bed inlet and outlet valves [V1 and V2] and open drain valve [V6] and vent valve [V5] to drain ATF from bed. After draining of ATF, close the drain valve [V6] and open side manhole to unload the used adsorbent. After unloading adsorbent, close the side manhole [6] and load the fresh silica gel adsorbent from top manhole [5].
Step-2 Process to Recover Surface Hydrocarbon:
As per Figure 2, take the used silica gel adsorbent into tank A and submerge with water. Circulate the water from bottom to top using pump, alternately air purging also can be used. Collect the floated hydrocarbon from top liquid layer of tank B and transfer it to slop oil system for reprocessing. Water washed adsorbent will be free from surface hydrocarbon hence it will reduce fuel loss, reduce chemical hazards, avoid adverse impact on environment by reducing volatile hydrocarbon release in air, therefore it will improve operational safety and easy for handling for regeneration or disposal. Also, it will make process more cost effective.
Step-3 Process to Regenerate Adsorbent:
As per Figure 3, take washed silica gel adsorbent into the regeneration furnace stainless steel vessel. Start the nitrogen purging using valve [V2] and start furnace temperature raising from ambient to 350 °C at the rate of 100 °C per hour. Initially water and adsorbed hydrocarbon get vaporised and get condensed at condenser and collected in hydrocarbon recovery vessel between 100 to 350°C. Once hydrocarbon recovery is over, switch the purging gas from nitrogen to air and start further raising of furnace temperature up to 700 °C, at higher temperature in presence of air oxygen, all hydrocarbon impurities will get decomposed or oxidized and adsorbent get regenerated. This process is recovering hydrocarbon and regenerating adsorbent hence it will reduce fuel loss, avoid generation of waste, avoid adverse impact on environment, therefore it will improve operational safety and reduce operational cost. Alternately, user can avoid step-2 and take directly feed from step-1.
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Various laboratory scale qualitative and quantitative experiments were conducted on actual ATF type petroleum distillate samples collected from crude oil refinery and silica gel adsorbent purchased from market. In this experimental study work following aspects are studied:
1) Development of process for thermal stability and water separation characteristic improvement in ATF type petroleum distillate.
2) Experimental work to check the effect on all quality parameters of ATF products.
3) Development of process for recovery of surface hydrocarbon from used adsorbent.
4) Development of process for regeneration of used adsorbent.
5) Experimental work at Laboratory scale.
6) Feasibility of invented process with respect to cost, availability of technology,
availability of material (adsorbent), operational safety, impact on environment and
easy implementation in the field.
Details of Equipment and Materials Used for Experimental Work:
Adsorbent: The different grades of white silica gel crystal purchased from market. Figure 4 represent the image of fresh white silica gel crystal that used as adsorbent. The technical specification of white silica gel is mentioned in the below table-2.
Table 2: White Silica Gel Specification

TECHNICAL SPECIFICATION
DESCRIPTION SILICA GEL WHITE
TYPE Non-Indicating
ASSAY(as SiO2),% 97-99
pH 5.5 - 7.0
Bulk Density, gm/ml 0.600 - 0.700
Loss on Drying,% 5 – 6
Adsorption Capacity at 100% humidity , % 27 – 35
Friability 99.5
Chloride (as Nacl),% Max 0.5
Sulphates (Na2So4),% Max 0.5
Ammonium Compound (NH3), % 0
Particle Size, mm 0 to 1, 1 to 2, 2 to 4 and 4 to 8
Chemical Formula SiO2 + H2O
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ATF: Samples of Aviation Turbine Fuel (ATF) were collected from M/s Nayara Energy petroleum refinery, Vadinar, Dist. Devbhoomi Dwarka, State - Gujarat, India.
Thermal Stability Analyser (Jet Fuel Thermal Oxidation Tester -JFTOT):
Instrument comply with the requirements of standard test methods viz. ASTM D 3241, IP 323 and IS 1448 Part 97 and make by M/s Expoteck USA, INC, Model -FALEX 400. Deposit Rater: Visual tube deposit rater and automated deposit rater comply with the requirements of standard test methods viz. ASTM D 3241, IP 323 and IS 1448 Part 97. The automated interferometry technique (ITR) makes by M/s AD Systems Model- DR 10 was used for deposit thickness measurement.
Micro-Separometer: Instrument comply with the requirements of standard test-methods viz. ASTM D 3948 and IS 1448, Part 142 and makes by M/s EMCEE Electronic INC, USA, Model 1140 Micro-separometer, Mark X.
Glass Wares: Glass Bottles (200, 500 and 2000ml capacity), cylinders (100, 500 and 1000ml), separating funnels, test tubes, volumetric flask etc. Balance for sample weight: 0 to 210 gm and 0 to 5kg.
Magnetic Stirrer: Capable to control from 0 to 500 RPM with magnetic needle. Adsorbent Glass Column: 500 ml capacity glass column as shown in figure- 5. Adsorbent skid: 10 lit capacity stainless steel (SS) skid as shown in figure- 7. Hydrocarbon Recovery System: Glass assembly for recovery of hydrocarbon from used silica gel by water washing as shown in figure - 9 and figure-2.
Adsorbent Regeneration System: Muffle furnace with heating capacity up to 1000°C and stainless steel (SS) 300 ml assembly with glass condenser and hydrocarbon receiver as shown in figure- 10 and figure-3.
Testing methods: Testing methods used are recommended by ATF standard product specifications.
The inventors have conducted various laboratory experiments to conclude the performance parameters of new process for improving quality of ATF type petroleum distillate. Out of many such laboratory experiments, some of important experiments are explained below for evidence and reference of laboratory experimental work. However, the scope of the invention should not be limited to said examples.
Experimental Work:
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1.1 Determination of Improvement of Thermal Stability by Silica Gel Adsorbent:
Aim: To check the effect of white silica gel on thermal stability of aviation turbine fuel.
Experiment Condition / Procedure: Aviation turbine fuel samples from different process stage (Salt dryer outlet, VGO MHC Kerosene and ATF tank) were collected and tested for thermal stability test at laboratory. Sample which was failed in thermal stability test were only used for this experimental work. ATF samples were passed through 300 ml white silica gel bed prepared in glass column at laboratory. Treated samples were tested for thermal stability test to see the improvements. The JFTOT heater tubes were rated by visual method as well as by interferometric method using AD System Deposit Rater-DR10. The observed test results of thermal stability are tabulated in below table 3.
Table 3: Thermal stability Test Results before and after silica gel treatment.

Sample Details Properties Thermal Stability before Treatment [A] Thermal Stability after Silica Gel Treatment [B] Improvement in Thermal Stability [B-A]
ATF Tank 351 C Deposit Rating by Visual Method >3, Abnormal <1, No Peacock or Abnormal Failed fuel become pass

Deposit Rating by
Interferometric Method by DR 10, Nanometres 119 21 98

Pressure
Difference,
mmHg 3 1 2
KMU Salt Dryer Outlet Deposit Rating by Visual Method >3, Abnormal <1, No Peacock or Abnormal Failed fuel become pass

Deposit Rating by
Interferometric Method by DR 10, Nanometres 173 18 155

Pressure
Difference,
mmHg > 25 < 1 24
VGO MHC Kerosene Deposit Rating by Visual Method >3, Peacock and Abnormal <1, No Peacock or Abnormal Failed fuel become pass

Deposit Rating by
Interferometric Method by DR 10, Nanometres 865 15 850
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Pressure

Difference, 3 1 2
mmHg
Observations: From the above test results, it is observed that, white silica gel is capable to improve thermal stability of aviation turbine fuel. Figure 2 represent the image of deposit on fresh heater tube [A], heater tube after passing of dirty fuel sample [B] and heater tube after passing of silica gel treated fuel sample [C].
1.2 Determination of Improvement of Water Separation Characteristic by Silica Gel Adsorbent:
Aim: To check the effect of white silica gel on water separation characteristic of aviation turbine fuel.
Experiment Condition / Procedure: Aviation turbine fuel samples from different process stage (VGO MHC Kerosene and ATF tank) were collected and tested for water separation characteristic using standard test method ASTM D 3948 or IS 1448 Part 142. Since, it is not possible to get samples with lower MSEP rating from process, above samples were doped with 1 gm per litre surface active agent (bis-2- ethylhexyl sodium sulfosuccinate also called Aerosol) to prepare experimental samples with lower MSEP rating at laboratory. The MSEP test was conducted before and after passing fuel sample through white silica gel bed to see the improvement. The observed test results of MSEP rating are tabulated in below table 4.
Table 4: Test results of MSEP rating before and after passing through silica gel

Sample Details MSEP Rating before Aerosol doping [A] MSEP Rating After doping 1gm / lit Aerosol [B] MSEP Rating after passing through Silica Gel [C] MSEP Rating
Improvement
[C-B]
ATF Tank 450 A 99 72 100 28
VGO MHC Kerosene 98 72 99 27
Observations: From the above test results, it is observed that, white silica gel is capable to improve water separation characteristic of aviation turbine fuel.
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1.3 Determination of Thermal Stability Improvement Efficiency of Silica Gel Adsorbent:
Aim: To check the thermal stability improvement efficiency of silica gel adsorbent.
Experiment Condition / Procedure: Aviation turbine fuel samples were collected from Kerosene Merichem Unit (KMU) salt dryer outlet and tested for thermal stability test. To check the thermal stability improvement efficiency, take 700 ml fuel sample in glass container and added white silica gel, keep the container for four hours with stirring at ambient temperature. After filtration, fuel samples were tested for thermal stability test. The heater tubes were inspected by interferometric method using AD System Deposit Rater-DR10. The observed test results of thermal stability are tabulated in below table 5. The fuel sample volume, weight of silica gel and thermal stability data are used to calculate thermal stability improvement efficiency of silica gel. Thermal stability improvement efficiency of silica gel is calculated using below mentioned formula: Thermal Stability Improvement efficiency [E] = ((C-D) X A) / B nanometers deposit thickness per millilitre of ATF per gram of silica gel adsorbent
Table 5: Thermal stability improvement efficiency of silica gel

Sample Details ATF Volume in ml [A] Weight of
Silica Gel in
gm [B] Initial ATF,
Deposit
Thickness in
Nano Meter
[C] Treated ATF,
Deposit
Thickness in
Nano Meter
[D] Thermal
Stability
Improvement
efficiency [E]
Sample-1 700 0.7005 173 62 110921
Sample-2 700 0.5022 148 86 86420
Avg. Value - - - - 98670
Observations: From the above test results, it is observed that, white silica gel is having thermal stability improvement efficiency around 99000 nanometers deposit thickness per millilitre of ATF per gram of silica gel adsorbent.
1.4 Determination of Relative Thermal Stability Improvement Efficiency of Silica Gel and Attapulgite Clay:
Aim: To check the relative thermal stability improvement efficiency of Silica Gel and attapulgite clay.
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Experiment Condition / Procedure: The ATF samples, experimental conditions, deposit testing method and efficiency calculation are used same as earlier experiment in the main application. In this experiment, ATF samples were treated with attapulgite clay collected from KMU. The observed test results are tabulated in below table 6. The thermal stability improvement efficiency of clay is calculated and compared with silica gel to check the relative thermal stability improvement efficiency.
Table 6: Thermal Stability Improvement efficiency of Clay

Sample Details ATF Volume in ml [A] Weight of
Clay in gm
[B] Initial ATF,
Deposit
Thickness in
Nano Meter
[C] Treated ATF,
Deposit
Thickness in
Nano Meter
[D] Thermal
Stability
Improvement
efficiency [E]
Sample-1 700 0.7002 173 41 131962
Sample-2 700 0.5019 148 81 93445
Avg. Value - - - - 112703
Calculation for relative thermal stability improvement efficiency % of silica gel compared to attapulgite clay: (99000*100)/112700 = 88.4
Observations: From the above test results, it is observed that, attapulgite clay is having thermal stability improvement efficiency around 112700 nanometers deposit thickness per millilitre of ATF per gram of attapulgite clay adsorbent. The relative thermal stability improvement efficiency of silica gel compared to attapulgite clay is around 88.4 percent.
1.5 Determination of effect of silica gel on other key properties of ATF.
Aim: To check the effect of silica gel on other key properties of ATF.
Experiment Condition / Procedure: The ATF sample was collected from tank 61-T-351 C and tested for all key properties specified in ATF standard specification DEF STAN 91-091 / IS 1571 and few additional parameters before and after silica gel treatment to check the adsorbent effect on quality of ATF. The observed test results of all tested key properties are tabulated in below table 7.
Table 7: Test results of ATF key properties before & after treatment

Parameters Unit ATF Tank 61-T-351 C

Before Treatment After Silica Gel Treatment
Colour by Tintometer Saybolt +10 +30
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Density @ 15 °C gm/ml 0.7866 0.7860
Flash Point °C 39.5 40.0
Marcaptans (RSH) % Wt. 0.0014 0.0014
Sulphur % Wt. 0.2543 0.2484
Distillation
IBP °C 148.1 147.6
10 % Vol.
164.1 163.1
50 % Vol.
180.0 179.2
90 % Vol.
205.1 203.8
FBP
226.0 224.5
Residue % Vol. 1.1 1.0
Loss % Vol. 0.6 0.6
Freezing Point (ASTM D-5972) °C -67.6 -66.0
Smoke Point (Auto) mm 25.7 26.0
MSEP Rating 94 100
JFTOT-Tube Rating by Visual Method (VTR) Rating >3, Abnormal <1, No P/A
JFTOT-Pressure Differential mmHg 3mmHg 1mmHg
JFTOT- Tube Rating by Interferometric (ITR) Method, Deposit Thickness) nm 119 21
Total Aromatic % Vol. 16.1 15.6
FAME Wt. ppm <4.5 <4.5
Naphthalene % Vol. 0.31 0.29
KV @ -20°C mm2/s 2.912 2.906
Total Acidity mgKOH/gm 0.002 0.0014
Gum Content mg/100ml 1 1
Cu Corrosion @100°C, 2hrs Rating 1a 1a
Conductivity @ 25°C ps/m 26 1
Metal Elements Wt. ppm
Fe / Ni / V
<0.1/<0.1/<0.1 <0.1/<0.1/<0.1
Cu / Si / P
<0.1/<0.1/<0.1 <0.1/<0.1/<0.1
Zn / Mg / K
<0.1/<0.1/<0.1 <0.1/<0.1/<0.1
Al / Ca / Pb
<0.1/<0.1/ 0.2 <0.1/<0.1/ 0.3
Water Wt. ppm 108 96
Nitrogen Wt. ppm 2.2 0.5
Observations: From the above test results, it is observed that, white silica gel is improving ATF properties namely saybolt colour, thermal stability, water separation characteristics, moisture content and nitrogen content. There is no negative impact observed on any of tested properties except conductivity, which can be maintained by addition of additive.
2. Experiments for Used Silica Gel Adsorbent:
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Aim: To develop process for recovery of surface hydrocarbon and regeneration of used silica gel adsorbent.
To achieve above aspects, following experiments were done using used silica gel, Figure-8 represent the image of used silica gel collected after field trial.
2.1 Recovery of Surface Hydrocarbon from Used Silica Gel Adsorbent:
Aim: To develop process for recovery of surface hydrocarbon from used silica gel.
Experiment Condition / Procedure: Laboratory scale experiments were carried out using used silica gel in glass assembly, water was circulated from bottom to top and floated hydrocarbon volume was measured. The hydrocarbon concentration calculated and tabulated in below Table-8. Figure -2 & 9 represent the image of laboratory scale surface hydrocarbon recovery system. Figure 11 represent the image of recovered hydrocarbon.
Table 8:

Used Silica Gel, Wt. in gm Hydrocarbon Recovered in ml Hydrocarbon Recovered in % Vol. / Wt.
100 14 14
150 17 11
Hydrocarbon Recovery from Used silica Gel.
Observations: From the above test results, it is observed that, used silica gel is having considerable amount of surface hydrocarbon in the range of 11 to 14 % Volume per weight of used adsorbent and simple water washing process can recover the same. The recovery of surface hydrocarbon from used silica gel will have many benefits for downstream activities like, regeneration or disposal of waste adsorbent,
a) It will reduce hazard contamination hence handling of waste will be safe.
b) It will recover hydrocarbon hence will reduce fire hazard, reduce releasing of volatile organic matter in air, and also reduce quantity of waste.
c) Recovered hydrocarbon will be reprocessed hence will realize fuel price from waste.
d) Water washed silica gel can be either send for regeneration or disposal.
2.2 Regeneration of Used Silica Gel Adsorbent:
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Aim: To develop process for regeneration of used silica gel along with recovery of hydrocarbon.
Experiment Condition / Procedure: Take used silica gel (after water washed or without water wash) in laboratory scale regeneration assembly as shown in figure- 10. The laboratory scale experiments were conducted to verify the process performance using muffle furnace at 700 °C temperature, nitrogen / air flow 400 to 500 ml per minute, run time 100 minute in batch process. The observed test results are tabulated in below table-9. Figure- 3 & 10 represent the image of laboratory scale regeneration system, Figure-8 represent the image of used silica gel, figure-12 represent the image of regenerated silica gel and figure-11 of recovered hydrocarbon oil during thermal regeneration.
Table 9: Regeneration of used Silica Gel by Thermal air oxidation with recovery of hydrocarbon

Silica Gel Details Silica Gel Wt. In gm Recovered Hydrocarb on In gm Recovered Hydrocarbon In % Vol. /Wt. Appearance of regenerated silica gel
Used silica gel with water washed 100 4 4 Dark brown silica gel become slight brownish white
Used silica gel without water wash 93.4 21 22.5

Used silica gel without water wash 100 21 21

Observations: From above test results, it is observed that used silica gel can be easily regenerated by thermal air oxidation. The process is also recovering considerable amount of hydrocarbon (surface and adsorbed) up to 22.5 % volume per weight of adsorbent. The process is avoiding generation of waste as well as avoiding loss of precious hydrocarbon oil hence it make process more economical.
2.2.1 Quality of Recovered Hydrocarbon:
Aim: To check the quality of hydrocarbon oil that recovered from water washing or thermal regeneration process.
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Testing of Quality Parameters: The recovered hydrocarbon oil was tested for key quality parameters and observed test results are summarised in below table-10. Figure 11 represent the image of recovered hydrocarbon oil.
Table 10: Quality of Hydrocarbon Oil Recovered from Water Washing or Thermal Regeneration

Quality Parameters UOM Test Results
Density at 15 Deg. C gm/ cc 0.81 to 0.82
Total Sulphur % Wt. 0.66 to 0.84
Total Organic Nitrogen ppm Wt. 1200 to 2000
IBP Deg. C 68 to 78
FBP Deg. C 302 to 366
Observation: Above quality information of recovered oil can be useful for reprocessing of recovered hydrocarbon with refinery slop oil.
Advantages of the Invention:
The present invention is globally applicable to crude oil petroleum refining industries to improve Saybolt color, improve stability of Saybolt color, reduce organic nitrogen content, and reduce moisture content of kerosene type petroleum distillates. Furthermore, present invention also useful to recover hydrocarbon from used adsorbent and regenerate used adsorbent, hence present invention has many benefits to crude oil refining industries. Based on various experimental test results and observations, following benefits are envisaged:
1) Invented process is capable to improve thermal stability of aviation turbine fuel.
2) Silica gel is capable to improve up to 99000 nanometers deposit thickness per millilitre of ATF per gram of silica gel adsorbent.
3) The thermal stability improvement efficiency of silica gel is comparable with attapulgite clay.
4) Invented process is capable to improve water separation characteristic of aviation turbine fuel.
5) Invented process can be alternate to attapulgite clay process.
6) Silica gel is produced synthetically hence quality remains constant compared to attapulgite clay.
7) Silica gel can be regenerated and reused while clay can’t.
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8) Clay become muddy in presence of water while silica gel can’t, hence it will not increase back pressure.
9) Silica gel can be used in bottom of clay bed to avoid mudding which make easy unloading of adsorbent from bed.
10) Silica gel can be blended with clay to improve ATF manufacturing process performance with respect to thermal stability, water separation characteristic, saybolt colour and saybolt colour stability etc.
11) Invented process is capable to recover surface hydrocarbon up to 14% volume by water washing.
12) Invented process is capable to recover surface and adsorbed hydrocarbon up to 22.5% volume by thermal regeneration process.
13) Invented process is capable to regenerate adsorbent, hence it is avoiding generation of hazardous waste.
14) Adsorbent used in process is easily available in the market at reasonable cost hence process is feasible and cost effective.
15) Invented process is recovering hydrocarbon and regenerating adsorbent, hence process is become more economical.
16) Invented process is operated at ambient temperature and pressure hence it is easy and safe to operate in the field.
17) The recovered hydrocarbon can be reprocessed; hence it will realize fuel price from waste.
Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present invention as defined.
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We claim:
1. A novel process for improving thermal stability and water separation characteristic of
aviation turbine fuel (ATF) type petroleum distillates, the process comprising:
i. passing ATF type petroleum distillate through silica gel adsorbent bed;
ii. recovering surface hydrocarbon from used silica gel by water washing; or
recovering surface and adsorbed hydrocarbon by thermal regeneration; and iii. regenerating used silica gel obtained after Step-1 or after Step-2 by thermal
oxidation.
2. The process as claimed in claim 1, wherein step ii, is optional.
3. The process as claimed in claim 1, wherein step ii and iii, are optional.
4. The process as claimed in claim 1, wherein the thermal oxidation comprises:
i. raising furnace temperature from ambient to 350°C at the rate of 100°C per hour
while purging nitrogen; ii. switching purging gas from nitrogen to air and raising furnace temperature up to
700 °C.
5. The process as claimed in claim 1, wherein the process improves thermal stability of ATF,
improves water separation characteristic of ATF, recovers hydrocarbon from used silica gel and regenerates used silica gel.
6. The process as claimed in claim 1, wherein the efficiency of thermal stability improvement is 99000 nanometers deposit thickness per millilitre of ATF per gram of silica gel adsorbent.
7. The process as claimed in claim 1, wherein the silica gel is blended with additional adsorbents.
8. The process as claimed in claim 1, wherein the silica gel is blended with attapulgite clay to improve the process performance with respect to thermal stability, water separation characteristic, saybolt colour and saybolt colour stability.