Tallinn University of Technology


Work objectives

The aim of this work was to carry out a comparative analysis of the properties of the oil-shale ashes of different origin from the point of view of their use, as well as taking into account environmental aspects. To this end, both literary data were assessed and real properties of ashes of different origin were compared, in particular in terms of chemical composition and leaching.

Main conclusions

1. General positions.

  1.1. Oil-shale ash is both a problem and an opportunity at the same time.

 1.2. There is no single concept of oil-shale ash. There is always a distinction to be made between the ways in which the ashes are obtained, as well as between the age and the methods of deposition.

  1.3. Oil-shale ash is not officially a hazardous waste.

2. There are many literary references to the various aspects of oil-shale ashes, both in the field of patent literature and scientific research. Their real assessment of future use should be based on the following basic criteria:

  2.1. whether it is a high-volume production (for example, building materials) or a niche product (for example, chemical products);

  2.2. whether the ash goes directly into the use or production process or whether the pre-treatment of the ash is required and what is its energy consumption and cost price;

  2.3. whether additional chemicals (such as granulation agents) are needed when making an ash product, how available they are and what their cost is, if necessary, the possibility of regeneration and its cost.

3. In practical use, only fresh ash directly from the process of its obtaining can be found, that is, one narrow fraction of ash separated from the electric filter, from the pulverized fuel-fired process, which will no longer be formed in the near future due to the closure of the pulverized fuel-fired boilers. The use of the solid heat-carrier method in the oil production process cannot be found at all, except for the role of the heat-carrier.

4. When comparing the composition of oil-shale ash and the concentrations of leaching compounds, the natural content of the corresponding element in the soil or Earth's crust should always be taken into account. Therefore:

  4.1. to avoid undue expectations, studies show that ash from kukersite shale is not a potential source of metals in the future;

  4.2. the content of metals separated during the leaching of oil-shale ash does not differ significantly from its natural background, which means that the level of ash hazard should not be artificially increased if this is not taken into account.

5. From an environmental point of view, oil-shale ash deposits would have to take into account in practice the ability of the ash to capture carbon and, based on relevant studies, the impact on achieving carbon neutrality and reducing the proportion of relevant CO2 quotas.

The study was carried out by the Oil Shale Competence Center of Taltech Virumaa College in 2017-2019 through the project "Oil Shale Competence Center" supported by the European Regional Development Fund. A summary of the study can be found HERE.

Brief summary of the research

Initial concept of the project

The co-processing of oil shale with organic materials, such as tire chips, is a well-known process. At the initial level of basic research, it has been proven that in the retort, oil shale also works with some other organic materials. Although the retort provides an overview of the ongoing fundamental process, it does not provide an adequate picture of co-pyrolysis, where the reaction products are removed from the system, that significantly limits the possibility of secondary reactions between the processing products.

Purpose of the work

To optimize the process of thermal processing of oil shale via co-processing and to find additional applications for materials that are still classified as waste.

Execution of the work

Since a large part of Estonian plastic waste goes either to landfill for storage or to incinerate as waste fuel, different types of waste plastic were selected for the first co-processing research, including sorting plastic waste extracted from the old landfill as a new direction. Landfill mining is also one of the future trends of waste management.

The research methods were selected from the standard retorting used for oil shale in the Fischer retort, which provides a good opportunity to compare the co-processing with the retorting of the basic shale, and thermogravimetric measurements, which allow the properties of the different mixtures to be quickly compared.

In addition to the existing technology, the material to be co-processed should adapt as much as possible to the operational parameters in order to avoid adjustments and to have a minimal impact on the quality of the resulting oil from the point of view of its marketing.

But these restrictions should not be followed during research. A successful co-processing can also be applied to lower-powered, more universal pyrolysis plants such as Petroter or Enefit.

Although in principle it is possible to make pyrolysis or low-temperature carbonization(semi-coking) of plastic waste without adding oil shale, the process is capricious and greatly depends on the equipment used and the technical execution of the process. Co-pyrolysis should increase the stability of the process.


1. During the research, it was first found that the addition of oil shale to plastic up to 50% stabilizes the process of semi-coking. At the same time, it should be taken into account that along with the oil shale, the material (in the form of the inorganic part of the oil shale), which is not directly converted into oil, is also included in the co-processing mixture.

2. Based on the results obtained, it was decided to find out which oil shale components - both inorganic and organic, have an impact on the process. In essence, in addition to oil shale co-processing, this meant finding out the possibilities of using residual materials from the shale industry.

Co-processing was investigated to study the impact of inorganic component:

  • power plant (fluidized bed combustion technology) with fly ash (a material similar to a solid heat-carrier);
  • power plant (fluidized bed combustion technology) with furnace ash (solid heat carrier-like material);
  • with residual coke obtained by GSK semi-coking (possible recovery of waste);
  • with sand (assumed inert material, component often present in the same waste);
  • with limestone (crushed stone made from it was used as the closest material to the inorganic part of the oil shale).

To study the effects of the organic part, tests were carried out on a mixture of kerogen (90 %) and plastic, which significantly increases the proportion of the organic part of oil shale in the mixture.

3. The research revealed that inorganic materials (from sand to oil shale ash) and organic components (from semi-coke to kerogen) can be involved in the co-processing process. The best results were achieved when using shale ash and semi-coke, where to achieve process stability the contribution of the inorganic component may be the lowest and, therefore, the potential oil yield is the highest.

4. The plastic material and the inorganic component should be mixed under conditions where melting and intensive pyrolysis of the plastic component do not occur simultaneously, i.e. mixing of the components should take place at relatively low temperature.

5. Based on the results of the study, an application for an intellectual property protection document has been submitted to the Estonian Patent Office.

6. In order to implement the process of co-processing in practice, it is necessary to continue applied research to solve technical problems.

The research is supported by the measure "Strengthening Regional Competitiveness" within the framework of the "Development of Regional Competence Centers" program under the project "Oil Shale Competence Center".

Brief summary of the study

Study background

The need to study the composition of shale oils has been an important factor throughout the history of shale oil production. Both tunnel oven and generator oils as well as those produced by the solid heat carrier process have been studied. Tightening requirements on the quality of shale oil (including sulfur content) dictate the need to find optimal shale oil purification methods. Possible applications of fine chemistry, practical application of co-processing methods and environmental constraints lead to changes in technological processes and, consequently, changes in the composition of oils. Therefore, it is extremely necessary to know the composition of the oil to the level of the individual compound.

Current state-of-the-art fuel composition detection devices (Phiona/PONA) are reliable for petroleum-based oils, but may distort the results for oils of other origins.

Main objective of the study

To develop an analytical solution that would allow at least semi-quantitative assessment of the oil composition to the level of a single compound by a fairly simple method. In this work, shale oil obtained by pyrolysis from oil shale of Estonian and Jordanian deposits, and oil obtained from used tires, were studied.

Research methods

Rectification and column chromatography, mainly gas chromatography (GC) and chromatomass spectrometry (GC-MS), were used to study the oils

Key results:

  1. The method of rectification into narrow fractions with subsequent determination of the group composition was not optimal, since polymerization during heating distorts the actual data on the composition of the oil.
  2. In order to avoid condensation of unsaturated compounds in pyrolysis oils during fractional distillation, a column chromatographic separation of the total shale oil into the groups of compound was performed.
  3. A method of fractionation of shale oil into compound groups using various solvents in a chromatographic column has been developed. The method of separating shale oil has been submitted to the Estonian Patent Office for obtaining an intellectual property protection document.
  4. When using this separation scheme for different oil shales, the composition of the shale oil group should always be taken into account; this method is only suitable for oxygen-rich oil shales.
  5. The column chromatographic separation tests of the total oils showed that the separation method developed is suitable for the total oil, i.e. it is also possible to divide the total oil into different compound groups. Thus, prior fractional distillation may be omitted for pyrolysis oils. This makes subsequent chromatographic analysis easier and saves from cumbersome recalculations.
  6. The content of phenols in the oil obtained from the solid heat carrier process was determined. To determine their potential, they must first be obtained from the oil as selectively as possible. This is the subject of follow-up research.
  7. It was shown that the quantitative determination of sulfur compounds in the shale gasoline by the gas chromatography method requires the use of an internal standard calibration method. Data obtained by the normalization method are not reliable.
  8. It was found that the arithmetic mean of GC-MS errors is -1%; The average arithmetic value of GC-MS absolute errors is approximately 14% of the total of the components studied. No systematic errors were detected, values were divided on both sides of the zero line (-50 ÷ +40 %). The relative error of the GC method is less than 7 %.

The research is supported by the measure "Strengthening Regional Competitiveness" within the framework of the "Development of Regional Competence Centers" program under the project "Oil Shale Competence Center".

Project background and purpose

When shale crude oil is fractionated, a light fraction is formed, called shale petroleum gasoline or, more briefly, shale gasoline. It consists of compounds with the lowest boiling point (mainly hydrocarbons). This is an intermediate product that is not used without further processing, that is, it is the starting material for the production of high-grade fuel.

For effective processing of raw materials, it is necessary to know its composition. Since shale gasoline is in many ways similar to petroleum gasoline, attempts have been made to determine its component composition according to Standard ASTM d6729 for petroleum gasoline analysis. However, the Standard ensures a true and valid result only within the scope of the uses specified therein. Shale gasoline is not included in the scope of the uses of ASTM D6729 Standard.

Thus, without further control, the Standard ASTM d6729 (for petroleum gasoline analysis) cannot be used. Verification of the method revealed that the analysis of shale gasoline by this method produces inaccurate results (inaccurate concentrations of compounds, misidentified compounds) and a large number of unidentified compounds.

This is due to technological differences in the production of petroleum gasoline and shale gasoline. To become a finished product, petroleum gasoline goes through a series of stages of purification and processing. Thus, the final product becomes a stable and substantially simplified saturated hydrocarbon mixture. At the same time, shale gasoline has only undergone the primary purification stage – rectification and therefore contains a significantly wider spectrum of compounds.

The aim of this work was to find a suitable methodology for the analysis of shale gasoline based on ASTM D6729 and to test it in practice for the study of the shale oil storage process.

Execution of work

Choice of apparatus

In accordance with the current Standard ASTM D6729, the composition of petroleum gasoline is determined by gas chromatography. To obtain adequate comparison results, the device was adapted to the requirements of the Standard and an independent control method, known as chromato-mass spectrometry, was used.

Comparative analysis of petroleum and shale gasoline

The physical-and-chemical parameters of both initial products were determined, which are relevant for the selection of the conditions for carrying out the analyses. The parameters for carrying out the analysis were then specified in order to obtain the results of the analyses under adequate conditions.

Specification of the composition of shale gasoline

The main part of the work was to clarify the composition of shale gasoline by mass-spectrometry and column chromatographic methods. The latter was used to divide the compounds into groups (alkane hydrocarbons, aromatic hydrocarbons and oxygen compounds) in order to get a more accurate picture of the content of the compounds with a lower concentration that would otherwise be below the limit of determination in the analysis of total gasoline. It was found that in low concentrations, shale gasoline contains a large number of different saturated and unsaturated hydrocarbons, as well as aromatic hydrocarbons. The oxygen compounds are mainly represented by various aliphatic ketones, but do not contain ethanol or aliphatic ethers, which are added to the commodity benzine as a component of bio-origin.

Verification of the analytical method

Subsequently, analyses of both products were performed both by Standard ASTM D6729 and mass spectrometry. In addition, standard test mixtures were used. As a result of the clarification of the conditions of the analysis and the methods of interpreting the results, a method for determining the component composition adapted to shale gasoline based on Standard ASTM D6729 was developed and finalized as a working rule.

The obtained result

The method makes it possible to provide research on the composition of shale gasoline for companies and researchers who need such studies. For example, if changes in the long-term storage of shale gasoline (resinification) are investigated or the quality of shale gasoline is determined.