Sludge Processing

Sludge Processing


Introduction to the Semfa sludge processing approach and philosophy

  • Oil sludge has been and is a major issue environmentally around the world and as part of the circular economy various technical and market innovations are leading the way in how the industry handles the sludge and processes it into conventional and more advanced and saleable products as part of the circular economy.
  • Each project is individually assessed, and the project is built around the parameters set by the sludge owners combined with the technical feasibility of the project objectives and logistics.
  • Semfa has been involved in various sludge processing projects over recent years with several partners and has a wealth of experience in assessing optimum theoretical outputs, advising on the most advanced and reliable technical partners and all other aspects of sludge processing.
  • Semfa has a well proven range of ancillary technologies for other hydrocarbon waste products as part of its environmental circular economy approach towards products such as used lubricants, marine oils and other similar products and is also working on a solution towards steel manufacturing waste such as coal tar as well. Naturally Semfa also offers, through its regional partners land rehabilitation strategies such as bioremediation, thermal desorption to meet land return to production or for construction.

Where necessary Semfa can, through its associations with well respected global inspection companies , offer internal and external inspection of tanks and storage facilities as part of a complete service to the sector.

Locations of typical oil sludge:
  • These can simply be in refinery and oil storage tanks where the sludge has settled over a period, sludge pits and lagoons as well as sludge lakes in remote areas.
  • Also, they can be found in areas where there have been pipeline leaks and other areas of accidents (more details of the solutions for this area are in the following parts of this section).

Oil Storage Tanks:

Pits, lagoons, and sludge lakes:

  • In all these cases, Semfa has developed strong partnerships with reliable and “state of the art “equipment manufacturers, project managers and assessors as well as contractors as part of a holistic approach to the issue of oil sludge processing.
  • In cases where land rehabilitation is required, Semfa also has partnered with leading regional contractors who specialise in this process with technologies from bioremediation through to thermal desorption.
Importance of analysing the oil sludge to the whole process:
  • No two sludge tanks, lagoons, pits, or lakes are the same composition and can have various amounts of water in them as well as carbon chain distribution (light or heavy hydrocarbon chains) which will naturally affect the processing outcome and economics. Therefor Semfa and its partners are clear about their approach to the whole area of sludge processing. No approach or recommendations will be made without firstly assessing the location, size of pits as well as the chemical make-up of the sludge itself. In this way a professional and realistic assessment and proposal can be made, and then realistic output predictions can be made as well as an economic plan.
  • To achieve this objective of assessing the sludge composition, Semfa has partnered with a specialist laboratory, who offer this paid service which will be refunded once the project has been initiated. In cases where logistically it is not possible or practicable to do this, Semfa and its partner laboratory will develop a cooperative arrangement with a local laboratory to undertake all tests and provide an assessment tool to undertake the analysis properly.
Geographical operations:

Semfa has several partners operating in specific markets together with teams who have a wealth of experience in the general area of sludge processing and each project will involve a combination of these groups and experts dependent upon the specifics of the project as well as availability. Semfa specialises on working with serious dependable partners and suppliers with a long-term vision and experience. Naturally these will depend upon the specifics of the project and the working environment.

Semfa New Strategic Alliance Semfa-PSI:
  • Semfa has now also signed a strategic alliance with an advanced processing technology group which processes oil field sludge straight into a range of products including EU standard # 5 gasoline and diesel as well as other products such as bitumen and others. These mobile refineries reduce several processing cost centres and therefor increases margins as well as reduces emissions and opens new approaches to sludge processing for the future.
  • This technology also has solutions to waste lubricants and fuel and therefor offers new solutions to the market place which can be integrated into the operation with ease .

Introduction to Hydrocarbon Sludge Waste Processing:

Semfa, as consultants, project developers and initiators have within its global network, fully experienced and trustworthy partners for equipment, technology, services and all key aspects of this area of hydrocarbon sludge processing .

Semfa, within its network and associates, has a wealth of experience in hydrocarbon sludge processing which has been extended into other forms of hydrocarbon waste processing to include waste or used lubricants, heavy, marine, and power station fuels, steel coke waste and other similar areas. The whole approach covers cooperation with some of the leading global technology, equipment, and service companies with a range of proven technologies to cover most projects currently.

Overall, the goal of processing oil sludge is to recover as much valuable oil as possible, while minimizing the environmental impact of the waste materials and to develop a circular economy system for the waste itself.

The approach that Semfa has refined includes several features but including:

  • A full and proper review of the project parameters and the overall objectives of the project owner to ensure maximum fit between the objectives and technical feasibilities.
  • Review of the operational limitations and characteristics of the sludge itself by means of comprehensive testing and analysis of the sludge and suitability to meet the objectives of the project owner alongside the technical capabilities of the recommended processing solutions.
  • Delivery of the technology and comprehensive continuous monitoring of the installation, equipment performance and service team focus.
  • Monitoring of the output to ensure compliance to the required standard of output.
  • In some cases, a special or unique approach will be required (such as utilising advanced technology to process sludge into specific outputs and also, where applicable, to undertake this on an industrial scale in factory specially designed factory units). Semfa ‘s experience knowledge and global network is experienced enough to undertake this as a complete project.

Prior to concentrating on the variations of sludge locations (such as tanks and lagoons/pits), it is important to understand the nature of hydrocarbon sludge and the various approaches that can be taken to process the sludge itself. Without this stage being undertaken professionally and currently, Semfa will not proceed with any project opportunity.

Hydrocarbon Sludge characteristics in refinery and storage tanks

The characteristics of oil in refinery storage tanks may include high viscosity, asphaltene content, and the presence of water and sediments. Over time, the sediments and water can settle at the bottom of the tank, forming a sludge layer. This sludge layer can cause several problems, including decreased tank capacity, increased tank corrosion, and reduced oil quality.

Therefore, it is important to regularly remove the sludge from refinery storage tanks to maintain tank integrity and oil quality. Sludge removal can help prevent tank leakage, equipment failure, and production downtime. It can also improve the efficiency of the refining process and ensure compliance with environmental regulations.

Processing stages:

The processing of oil sludge in storage tanks typically involves several stages, including:

  1. Separation: This stage involves separating the oil, water, and solid materials in the sludge using centrifuges or other mechanical separation methods.
  2. Thermal Treatment: The separated solids and liquids are then subjected to high temperature treatment in a thermal processing unit. This breaks down the sludge into its individual components and converts the organic materials into reusable products such as fuel oil or gas.
  3. Chemical/Physical Treatment: Chemical and physical processes can be used to further break down the sludge, remove contaminants, and recover any remaining oil. This may involve the use of solvents, bacteria cultures, or other chemical agents.
  4. Disposal: The remaining waste materials, such as sand and soil, must be properly disposed of in accordance with local regulations to prevent environmental contamination.

Taking the sludge out of tanks:

Environmentally and from a health and safety point of view, this has to be undertaken with the maximum of compliance to the highest standards of health and safety and to ensure the process is complete. Semfa has a complete range of the latest technology equipment and systems to achieve this through its close cooperation with some of the leading global technology and equipment suppliers in the market today. Each project is unique and needs to be handled in that way and the Semfa approach is to maximise the fit between project owner objectives and realistic technical realities.

There are several no man entry techniques that can be used for processing oil sludge in storage tanks, including:

  1. Robotics: Remote control robots can be used to clean the tank and extract the sludge. These robots are equipped with cameras and sensors to navigate the tank and perform cleaning tasks.
  2. High-pressure water jets: High-pressure water jets can be used to break up and remove the sludge without the need for personnel to enter the tank.
  3. Vacuum trucks: Vacuum trucks are equipped with powerful suction lines and can be used to extract sludge from the outer surface of the tank without the need for personnel to enter the tank.
  4. Airlifting: Airlifting techniques can be used to remove the sludge from the tank floor without the need for personnel to enter the tank.
  5. Mechanical methods: Mechanical methods such as pumps, conveyors, and centrifuges can be used to extract the sludge from the tank without personnel entering the tank.

In all cases, the objective is to dewater the sludge (ensuring the hydrocarbon content of the water meets the project owners’ standards) and sent to the interceptors. Through its association with leading water treatment groups, Semfa can supply a range of proven solutions for treating the hydrocarbon content and offer systems to clean the water to potable drinking standards if required.

No intrusive NDT and ANDT inspection can be offered as an ancillary service being led by Ron Long (a recognised global expert in this area) for external and internal integrity checks in partnership with a number of leading global technology and service companies.

With regards the solids the objective is to separate all solids from the sludge (and ensure that hydrocarbon content meets the standards as well to ensure that it is within specification for disposal). The final sludge is either return the processed oil back to the refinery (ensuring that the BS and W figures are compliant) for blending with stock ready for processing or taking the processed hydrocarbon oil and processing it directly into EU 5 compliant gasoline, diesel, and bitumen.

A full check list is available once a project has been highlighted and key information provided

Hydrocarbon Oil sludge in lagoons, pits, and lakes

Sludge in these locations is more complex than in tanks as there are a much larger unknown areas which need clarification prior to making proposals and developing the project.

Naturally a full and complete analysis of the sludge in each location needs to be taken (at various depths and parts of the pits) to our testing specification. Without this Semfa will not proceed with a project as stated above.

Additional areas for consideration include (but not exclusively) includes:

  • Dimensions of the pit/lagoon and type of construction.
  • Details of the wall construction and of any plastic sheeting specification
  • Estimated volume of sludge in the pit/lagoon and the condition of the sludge itself 
  • History of the pit/lagoon in terms of previous sludge processing, details of the source of the sludge.
  • Plan of the site highlighting access points, other sludge areas to be treated and power sources, proximity to interceptors, work area and hard stand, storage tanks and other key information regarding the site.
  • Overall target of the project owners with regards specification for the processed hydrocarbon oil, water, and solids as well as site clean-up preferences
  • Full details of any previous site clean-up and remediation technology utilised.
  • A full check list is available once a project has been highlighted and key information provided. 

Semfa views its involvement in this area and a real and serious focus and is committed to working with project owners to produce an on budget and target project with the most advanced technology available which is suitable for the location, operational parameters, and project owner expectations.

Semfa PSI sludge processing systems and solutions

Petroleo logo

As a direct result of over 15 years of research, development and refinement, PSI has built a strong business based on the strengths of the team involved in the technology of advanced sludge processing by utilisation of a mobile refinery concept. The combination of refinery and oil technologists together with chemical catalyst experts has led to a new way of processing hydrocarbon oil sludge.

The technology has been proven in full operation in several oil facilities and sludge locations and is now being marketed outside the Caspian region for the first time through the strategic alliance with Semfa covering a few regional markets.

The company has researched and developed a mobile micro refinery unit for the thermal catalytic cracking (TCC) processing of heavy hydrocarbons to produce components of light fractions of commercial petroleum products such as Euro-5 class fuels.

With a range of equipment and catalysts, the PSI system is focussed on offering specific end requirements for each project owner and developer, a tailor- made approach and also focussed on the chemistry and carbon chain distribution within the sludge itself which is a real advantage over other technologies for sludge processing. The philosophy is to ensure that the solution meets clients’ objectives, maximises the output and offers both mobile and fixed solutions to meet a range of client requirements.

This advanced technology has allowed the design and manufacture of a system which maximises resource-saving, is recuperative, environmentally friendly technologies and automated control systems, without the issue of solid - emissions and hazardous volatile fumes. This is clearly a solution for an environmentally advanced circular production cycle.

clean oil reccyling oil recycling

The PSI approach covers several stages:

  • Specific testing of sludge samples
  • Offering theoretical outcomes based on the sample analysis and recommending an approach to maximise output and client objectives.
  • Proposing a complete package including dewatering of the sludge, processing , sulphur treatment units and finally bitumen production units if this is required and sufficient heavy oil carbon chains are present in the sludge itself.
  • Full commissioning, on-site training and management if required to enable production to be initiated in addition to further process management and training programs as well as catalyst and chemical management and monitoring on site.
  • Possible provision of full-service packages as well.
  • Continuous monitoring and mentoring of the service operation to ensure consistency or performance, maximisation of output and efficiency of the overall operation.

The PSI Technology:

The technology is based on the use of a catalytic cracking evaporator reactor. The catalyst does not contain rare-earth and toxic metal salts.

Feedstock for processing is treated in the cavitation field, which, together with the catalyst is pumped into the evaporator reactor that leads to its evaporation followed by removal of cracking product vapours from the reactor to the cooler through the column.

The technology has been designed to have the ability to fractionate any heavy and viscous liquid hydrocarbons with maximum possible output. And has been developed to process a range of hydrocarbon- based materials (normally waste products) such as heavy paraffinic and high-viscosity bituminous oil, hydrocarbon liquids and oil sludge mixtures (sometimes which are contaminated by a wide range of contaminants and chemicals), lubricating oils, heavy waste oil mixtures, coal tar wastes, bunker fuels and polycyclic aromatic hydrocarbons (PAHs).

In general, and theoretical terms, the output of light oil fractions and products can range from 70% to 92%, depending on the physical and chemical composition of the feedstock.

The technology allows to maximize the output of EU 5 standard diesel and gasoline fractions due to the use of proprietary oil-soluble catalysts.

Bitumen from sludge as part of the PSI technology:

There is produced as part of the process via the oxidizing unit, an amount of high-quality construction or road modified bitumen (dependent upon the heavy hydrocarbon elements in the feedstock).

In some cases, where there is a significant amount of bitumen required for major long-term projects (for example ,as part of an import substitution program) a requirement for a fixed larger plant will be required and as such PSI have designed a plant to facilitate the production of significant volumes of bitumen where the right combination of heavy oils is also available to feed the plant.

The formulation can also be developed to include sulphur as a binder (which is a common way to reduce cost and increase performance) and other chemicals and plasticizers if required).

Bitumen from Sludge
The 4 stages of the PSI process:
  1. The first important part of the modular micro-refinery is the raw hydrocarbon catalytic treatment unit. This pre-treatment process helps to carry out mechano-chemical activation of raw materials with the process of breaking down the long hydrocarbon compounds molecules. This enables the provision of a rectification efficiency and thus maximize the output of finished petroleum products. By utilising an advanced catalytic system this will allow the recycling of a wide range of raw materials from crude oil to heavy hydrocarbons.
  2. The second part of the modular technology is a raw hydrocarbon portable micro-refinery unit with a production rate of up to 60 tons per day (3 shifts per 24 hours) . This smooth refining process is based upon a universal multi-purpose evaporation column (UPRA) to fractionate even an extra-heavy oil with a higher viscosity. The integration of the whole processing systems with a PLC/PAC computer-based control system allows for production on a 24/7 basis.
  3. The third part of the modular micro-refinery is optional depending on physical and chemical properties of raw hydrocarbons. Generally, it is well known that the heavier the crude oil, the greater its sulphur content which is an undesired contaminant in fuels and limited by the requirements of the EU5 specifications. To eliminate this problem supplies a desulfurization unit based on alumina catalysts filtration in various combinations with low operational costs and high-quality output.
  4. The final part of the modular micro-refinery is the tar residues oxidation unit to produce and modified high quality ( typically 60:70 standard) road and construction bitumen which can be packed into big bags or metal euro barrels once cooled and stable.

Semfa Sludge Specialties

Semfa has a range of specialty services and products to accompany sludge processing be they in tanks or from pits and lagoons which give the Semfa a holistic approach to hydrocarbon sludge processing.

Some of these are summarized below (but are not exclusive) and information can be provided upon request relating to specific projects and circumstances.

A: NDT/ANDT Inspection of storage tanks pipelines and other ancillary assets in the refinery and storage areas. Headed by a well-respected expert in inspection techniques, Ronald Long, Semfa can offer a range of inspection techniques which fully allow analysis of the external and internal conditions of the assets in partnership with some of the leading global groups in the industry which can be extended to other asset inspection aimed at the on shore and offshore oil. gas industries as well as chemical, fertilizers, and water industries. There is also an approach developed by Ronald to establish a sophisticated local inspection company to be partnered with one of the leading Global Groups to maximize local content under various Government initiatives, especially in “developing” nations. The package includes technology, equipment as well as full training programs and certification and can also include the provision of managers to commission and monitor the project.

B: Supply of contract workers, managers and project controllers can also be provided via LLR Global based in the UAE for many areas of operation in the oil and gas industry. This is aimed at developing countries where experience is required whilst training of local teams can be undertaken as part of a wider project. In some cases, full teams can be provided as part of a project in addition to contractors and contracting companies.

C: Bioremediation and land rehabilitation is a key area where cleaning up leaks, spills and problematic pits/ lagoons and lakes is concerned. This becomes very important where penetration of the hydrocarbons is an issue for aquifer contamination. Not only is the issue of cleaning the hydrocarbon pollution (which can be theoretically rescued and recycled) but also returning the land to productive use or making it suitable for construction or other matters. This whole operational area includes assessment of the situation and evaluation of the effect of the pollution, but also includes full repair, land cleaning and treatment as a project by well qualified and experienced partner groups. Semfa can also provide the establishment of an emergency contracting group to develop a locally based leak containment operation for on and offshore leak control, clean-up, and prevention.

D: Used oil, fuel oil, off specification fuels, lubricant and similar hydrocarbons are an issue for treatment and recycling and Semfa has a number of options and technologies which can be utilized to develop a quality an environmentally circular economy for many of these product groupings. The choice of the most suitable technology would be related to the specific project involved. The options are led by PSI with their mobile refinery technology which can be utilized to refine and reformulate many of these products and can be blended or used in fresh markets. Typical utilization options theoretically include (but not exclusively) the following:

  • Used lubricants and hydrocarbon-based oils can be processed into fresh lubricants for blending
  • Used heavy fuel oils, marine fuel and heavy carbon chain fuels can be processed into new EU # 5 standard gasoline and diesel as well as bitumen’s suitable for many applications such as roads and similar markets. In this case the refining process combines both the fuels and gasoline, and the ratio is a direct function of the carbon chain distribution.
  • Base stock for blending into fuels for various markets and product groups.

E: Local supply of fuels in isolated oil wells and operations can be achieved where instead of sending the hydrocarbon oil to the refinery via pipelines, it can be processed on site by the PSI mobile refinery unit and fuels either directly supplied to the surrounding area by tankers or to the refinery for blending by tankers as well.

Oil Refinery


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Founded in 1986 Semfa International Limited has developed a strong reputation for excellence in delivering advanced solutions to meet the highest of client requirements globally.

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