Performance Evaluation of Solvents Blend for Silicone Defoamer
Chapter One
Aims and Objectives
The aim was to produce defoamer using solvents such as diesel, kerosene, naphtha and palm kernel oil and their blends with silicone and check for their effectiveness in controlling crude oil foam formation.
The objective involves combining each of the solvent with silicone to produce defoamers.
CHAPTER TWO
LITERATURE REVIEW
Introduction
The control or elimination of the foam that arises in many industrial processes can be the crucial factor promoting smooth plant operation. Foam can waste capacity of processing vessels and can interfere with the efficiency of separation units. For these reasons, antifoams have become valuable process aids in a wide variety of industries. Aqueous foams stabilized by synthetic surfactants commonly occur in detergents such as those used in industrial textile processing and laundry operations. Design of the surfactant system for these applications is typically motivated by the need for enhanced cleaning performance and cost effectiveness, while providing an acceptable environmental profile. Oftentimes today’s highly foamy surfactant systems require the addition of antifoams to control foam formation. Modern antifoams are complex formulated specialty chemicals but generally consist of an insoluble oil phase containing hydrophobic solids dispersed within it. One commonly used oil for antifoams is polydimethylsiloxane (PDMS), which can be selected on the basis of viscosity and/or viscoelastic properties that are best suited to the application. The antifoam is typically provided in a delivery system such as an emulsion or dispersion, which liberates droplets of a controlled particle size and size distribution to the surfactant solution. (Jha et al., 2000)
Industrial problems caused by foaming
- Mechanical problem that may generate foam
-Leaky seals on pumps
-High pressure pumps
-Poor system design (tank, pump inlet, outlet and manifold design)
-Pressure release
The main classes of air that are of concern in mechanical systems are dissolved air which behaves as part of the fluid phase, except that it can come out of solution as small bubbles (entrained air). Entrained air consists of bubbles that are small enough to collect on top of a fluid.
Bubbles that have sufficient buoyancy to rise to the surface are described as foam
- Foam in process and coolant liquids: Foam, entrained and dissolved air that are present in coolants and process liquids, may cause various kinds of problems, including:
- Reduction of pump efficiency (cavitation)
- Reduced capacity of pumps and storage tanks
- Bacterial growth
- Dirt flotation / Deposit formation
- Reduced effectiveness of the fluid solution(s)
- Eventual downtime to clean tanks
- Drainage problems in sieves and filters
- Formation problems (i.e. in a paper mill it may cause the fibers to form imperfect sheet)
- Cost of replenishing the liquid
- Cost of entire material rejection due to imperfections
Defoamers
A defoamer or an anti-foaming agent is a chemical additive that reduces and hinders the formation of foam in industrial process liquids. The terms anti-foam agent and defoamer are often used interchangeably. In industrial processes, foams pose serious problems. They cause defects on surface coatings. They prevent the efficient filling of containers. A variety of chemical formulas are available to prevent formation of foams.
The significant property of a defoamer is that it is generally insoluble in the foaming medium and has surface active properties. An essential feature of a defoamer product is a low viscosity and a facility to spread rapidly on foamy surfaces. It has affinity to the air-liquid surface where it destabilizes the foam lamellas. This causes rupture of the air bubbles and breakdown of surface foam. Entrained air bubbles are agglomerated, and the larger bubbles rise to the surface of the bulk liquid more quickly. (Tarek 2015)
History of defoamers
The first defoamers were aimed at breakin g down visible foam at the surface. Kerosene, fuel oil and other light oil products were used to break down foam. Other vegetable oils also found some use. Fatty alcohols (C7 – C22) were effective but expensive antifoams. They were added to oil products to boost the efficiency. Milk and cream were forbears for modern day emulsion type defoamers. (Tarek 2015)
During the 1950s experiments with silicone based defoamers started. These were based on poly dimethyl siloxane (silicone oil) dispersed in water or light oil. Silicone oils worked well, but caused surface disturbances in many applications like paints and papermaking. In 1963 the first antifoams with hydrophobic particles (hydrophobic silica) in light oil were patented. In the early 1970s, hydrophobic waxes like ethylene bis stearamide dispersed in oils developed. These types of defoamers were very efficient, but the oil crisis of 1973 made these too expensive and resulted in a push for reduction of the oil content. The solution was adding water. So water extended (water in oil emulsion) and water based (oil in water emulsion) defoamers appeared. (Tarek 2015)
The development of silicone based defoamers has continued, using different emulsifiers and modified silicone oils. In the early 1990s, silicone emulsion defoamers that caused less surface disturbances were used in the wood pulping industry with great success. These caused better washing, reduced biological oxygen demand (BOD) in effluent and reduced deposits. (Tarek 2015).
CHAPTER THREE
MATERIALS AND METHODS
Materials
The materials used are:
- A pipette (10ml)
- Air sparger
- 500ml glass cylinder (2 pieces).
- 3litres of Crude oil emulsion or Surfactant solution if crude oil is used
- Solvents such as kerosene, diesel, refined palm kernel oil (RPKO) and crude palm kernel oil (CPKO) (100ml each).
- Silicone (500ml).
- Sample cans (20 pieces)
- 5 litre sample cans (5)
- Micro pipette
- Stop watch
- Hydrometer
- pH meter
Methodology
The method used for the defoamer test is the foam-rise or Bikerman test method
Procedures:
A fresh crude oil emulsion from the field was used.100ml of the crude oil emulsion was poured into the 500ml glass cylinder. The pipette which serves the same purpose of a glass capillary tube was inserted into the glass cylinder. One end of the air sparger was connected to the pipette while the other end is connected to the compressor. The air sparger system was operated for a fixed time (2mins), thereby blowing nitrogen gas/air through the pipette at a constant flowrate. The volume of foam generated immediately after 2mins of operation was measured as well as the volume of foam column that collapse after 30s. The time taken for the entire foam to collapse was recorded. This first run was regarded as result blank because it does not involve the addition of a defoamer.
The above process was repeated with the addition of 10, 15 and 20 µl volume of the defoamer products formed with each of the solvents combined with silicone in different proportions (20% silicone to 80% solvent/blend). The volume measurement was done by setting the micro pipette to measure the infinitesimal volume of the defoamer. The measured volume of defoamer was added to the 100ml crude oil sample for each case.
CHAPTER FOUR
RESULTS AND DISCUSSION
Results for defoamers and their components
Table 4.1 Physical properties of Defoamer components and the blends of the components (defoamers)
CHAPTER FIVE
CONCLUSIONS AND RECOMMENDATIONS
Conclusions
This research has enabled the combination of silicone with various solvents and its blends to produce different defoamers. The physical properties of the defoamers were also studied. Some of the defoamers were effective in the foam medium. The collapse rate required for the foam column to collapse served as the determining property for fast and slow defoamers.
Recommendations
The foamy liquid used in this research experiment was formed from the crude oil emulsion. From the analysed results defoamer B could be preferred among others in the crude oil flow station as an incentive against foaming. Defoamer B has the highest foam level reduction in 30secs when 15 ppm of it was added to the foam medium.
The effectiveness of these defoamers can also be tested in other foaming media apart from crude oil foams.
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