ALPHA OMEGA ZEOLITES FOR THE OILFIELD BRIEF

Transcription

1 ALPHA-OMEGA ALPHA OMEGA ZEOLITES FOR THE OILFIELD BRIEF ALPHA OMEGA ECOLOGICAL SOLUTIONS Athens Office: 8, R. Garibaldi & Sofroniskou str. Tel SKYPE PHONE: ALPHA OMEGA ECOLOGICAL SOLUTIONS Direct Phones: &

2 ZEOLITES FOR THE OILFIELD INTRODUCTION In recent years, attention has focused on the development of in situ (in place) immobilization methods that are generally less expensive and disruptive to the natural landscape, hydrology, and ecosystems than are conventional excavation, treatment, and disposal methods. In situ immobilization of metals using inexpensive zeolite, is is the most economical and ecological solution for remediation. This technique relies on a fundamental understanding of the natural geochemical processes governing the speciation, migration, and bioavailability of metals in the environment. In polluted soils, metals can be dissolved in solution, held on inorganic soil particles, complexed with organic soil components, or precipitated as pure or mixed solids. Soluble contaminants are subject to migration with soil water, uptake by plants or aquatic organisms, or loss due to volatilization into the atmosphere. Metals in soil may be associated with various phases that are reactive, semi-reactive or non-reactive. The risk to the environment from contaminated soil cannot be assessed by simply considering the total amount of potentially toxic metals within the soil because these metals are not necessarily completely mobile or biovailable. Natural zeolites are hydrated aluminosilicates, comprising of hydrogen, oxygen, aluminium, and silicon arranged in an interconnecting, open, three-dimensional structure. The primary building units are [SiO 4 ] and [AlO 4 ] tetrahedra linked together by oxygen atoms. Their crystal structure allows water molecules to be held and removed within the channels and cavities within the

3 lattice. These cavities can also contain exchangeable cations, in particular K, Na, Mg, Ca, Sr and Ba. The cavities and channels that exist within the zeolite framework can constitute as much as 50% of the total crystal volume (Passaglia & Galli, 1991), whilst water constitutes as much as 10-20% by weight of the natural zeolites (Mumpton, 1983). The presence and occupation of cations, within the cavities and channels will largely rule the amount of water contained within the zeolite framework. The general empirical formula, which represents a zeolite chemical structure, is shown below: M 2n O. Al 2 O 3. x SiO 2. y H 2 O M represents any alkali or alkaline earth cation, n the valence of the cation, x varies between 2 and 10, and y varies between 2 and 7 (Hawkins, 1983), with structural cations comprising Si, Al and Fe 3+, and exchangeable cations K, Na and Ca. Natural zeolites are not found as pure minerals. They can often contain small percentages of quartz, feldspar, clay minerals, cristobalite, calcite, gypsum and untreated volcanic glass. ZEOLITE PROPERTIES Ion Exchange The subsequent substitution of Si 4+ by Al 3+ leaves a net negative charge on the zeolite framework - known as Isomorphous Substitution. These areas of negative charge are therefore ideal sites for adsorption of exchangeable cations in solution. If there is no suitable site in the structure, or if it is already filled, the cations occupy the sites of water molecules upon ion exchange (Tsitsishvili et al., 1992). Molecular Sieves Zeolites also have the ability to exclude certain cations depending on their size; i.e. the size of the microporous channels and cavities within the zeolite structure can act to sieve cations. Those cations that are bigger than the internal cavities are excluded from all or part of the internal surface of the zeolite, whereas, cations that can fit into the internal structure can be exchanged (through isomorphous substitution or ion-exchange) onto the structure and become part of the zeolite framework. Hence, natural zeolites are renowned for their molecular sieve properties. Ion exclusion

4 phenomena are frequently observed in zeolites in which a particular ion is excluded from the exchanger because of its size (Townsend 1984). Ions can be partially exchanged because the volume the ion occupies may be too great, therefore occupying the intracrystalline space in the channels before complete exchange can be attained. Tsitsishvili et al., (1992) detailed that zeolitic water molecules act as bridges for framework ions and exchangeable ions in large framework cavities. This shows the mobility of these cations within the framework. Contaminated Land Remediation Natural zeolites have been shown to increase the soil cation exchange capacity and soil moisture, improve hydraulic conductivity, increase yields in acidified soils, and reduce plant uptake of metal contaminants in soil (Allen & Ming, 1995) ALPHA OMEGA ZEOLITE ALPHA OMEGA Zeolite is a benefit to the Oilfield Industry for a wide range of operations. Synthetic zeolite is currently used in gas plants for processing and water softening. Natural zeolite is used for environmental remediation (hydrocarbon & salt), reclamation (soil conditioning), drilling waste stabilization & encapsulation (leachate control), well casing cement, toxicity control, platform traction and produced water filtration (including CBM operations). Zeolite has tremendous potential in the oilfield industry. Natural zeolite is used for environmental remediation (hydrocarbon & salt), reclamation (soil conditioning), drilling waste stabilization & encapsulation (leachate control), well casing cement, toxicity control, platform traction and produced water filtration (including CBM operations). Reactive Permeable Barrier (RPB) technology involves the use of zeolite to capture and hold a variety of contaminants stemming from oilfield operations (ie: DNAPL, LNAPL, salts, metals, vapours, H 2S, etc ). This type of barrier not only prevents the migration of the contaminant plume onto adjacent property but also cleans the groundwater by acting as a filter thus eliminating the vapours and dissolved hydrocarbon in the groundwater. Many processes occur in the filter media (RPB) from sorptive processes (ad/ab), to molecular sieving, an oxygen source, and also as a biomass platform. The following is a simplistic view of the Zeolite RPB. Remember, the contaminant is held within the zeolite media as the groundwater

5 passes through it. Recall, zeolite has incredible cation exchange capacity and porosity thus enabling this natural filtration. Well Cementing Down-hole cementing operations for oil & gas industry have now introduced an innovative mixture involving high quality natural zeolite. Years of extensive research and field testing have produced a new light-weight cement technology. To provide financial perspective on this innovation, the worlds annual oilfield well cementing industry is worth $3 billion. The overview is this - the zeolite additive for traditional cementing applications provide for high-early strength with an adjustable density which leads to more perfect bond logs. This is due to zeolites capabilities for high water absorption while providing a low viscosity. This is the biggest breakthrough in cementing technology for the oilfield since foamed cement was introduced 30 years ago. Concrete Mix Design using Zeolite as a Pozzolan A pozzolan is a siliceous or siliceous and aluminous material, which in itself possesses little or no cementitious valve but will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties (ASTM) Cement consists of three types of materials: Limestone (CaCO 3), Aluminum silicate (clay or shale), and Inert materials such as sand and gravel. The limestone and clay are fired together in a rotary kiln. The limestone decomposes to lime (CaO) which reacts with the clay or shale to form clinker. Clinker consists of tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetra calcium aluminate ferrite. The clinker is finely ground generally in a ball mill to make cement. In Portland-pozzolan cement, 15% to 40% of the cement can be replaced by a Zeolite pozzolan. The definition of cation exchange capacity (CEC) of pozzolans for the concrete business is as follows: Typically pozzolans CEC range

6 from 19.1 meq/100g to 63 meq/100g while BRZ Zeolite CEC is 160 to 180 meq's/100g. Lightweight Cement & Aggregate Zeolites are naturally-occurring porous aluminosilicate Mine Tailings Treatment Zeolite provides a simple solution to the complex issue concerning mine tailings. Simple science using zeolite can reduce and eliminate these concerns. Zeolites are low cost ion-exchangers for the removal and recovery of heavy metals cations, particularly in acid mine drainage. They are used in four ways in order to treat heavy metals and mine waste: 1. Removal of metal cations in effluent/wastewater by Direct Filtration. ALPHA OMEGA Zeolite has a very high CEC as compared to other zeolites and will trap and hold the various metal ions (see the list below). Significant properties include: High cation exchange capacity Selectivity for many metals Low cost relative to resins or synthetic zeolites Capacity for regeneration 2. Soil remediation by Stabilization. This involves the application of zeolite directly into the contaminated soil in order to chemically bind the metal ions via cation exchange. 3. Soil remediation by Encapsulation. This involves a process of mixing the mine waste with water, zeolite, and cement in order to create a concrete block that passes TCLP1311 Leachability Testing. Currently, there are many environmental companies using this method to handle oilfield drilling waste. CONCLUSION Alpha Omega Zeolite can and will address the remediation of your soils and water contamination problems. Zorpas et al., (2000) found composting dewatered biosolids with the natural zeolite clinoptilolite decreased heavy metal content in the final compost. Through fractionation studies, researchers were able to show that the clinoptilolite readily took up the metal content bound in the exchangeable and carbonate fractions. It would

7 therefore seem an ideal solution to perhaps utilise natural zeolites with sludge before the biosolids are spread onto agricultural land, either before dewatering at the wastewater treatment plant, or through composting. One of the main advantages highlighted for pollution control and remediation is the regeneration of the natural zeolite. Once exhausted, regeneration not only allows for the continual use of the zeolite but produces a waste which is smaller in volume, easier to handle and in some cases the pollutants may be retrievable.