Paraho II™ Technology

From the Portuguese para hominem, or for mankind

Paraho II™ Technology

Paraho II™ is a multi-step, shale oil extraction technology that links numerous proven technologies occurring before and after the Paraho® retort and oil recovery systems. Today, Paraho II™ represents the technological advances that continue to evolve from the original application of the Paraho® process. STIS has developed many of these progressions and continues to make advances in retorting efficiency, environmental performance, and enhanced oil recovery. Key benefits of the Paraho II™ Technology are:

  • Availability—mechanically simple, Paraho II™ operates at industry leading online uptime.
  • Adaptability—multiple modes of operation provide the highest possible shale oil yields over a variety of shale types.
  • Safety—low operating pressures, thermal encapsulation, and few moving parts help create a safe operating environment.
  • Energy Efficiency—recovers and uses heat from thermal waste streams to reduce operating expenses.
  • Environmental Performance—our waste streams are typical of other thermal processes and are managed through use of comparable control technologies.

The Paraho II™ Technology is comprised of two major sub-systems: The Paraho® Retort and the Paraho® Oil Recovery System.

The Paraho® retort is a refractory lined, vertical shaft kiln capable of retorting a wide range of shale types, from carbonate to silica based shales.

Process Overview

Feeding the Ore to the Retort

Shale from a crushing and screening plant is fed into the top of the vertical retort and flows downward, by gravity, as a continuous moving bed.

Heating the Ore

The ore is progressively heated by upward flowing gases as it descends through the retort until the shale reaches pyrolyzing temperatures.

Kerogen Breakdown

The kerogen in the shale breaks down into oil vapor, gas, and carbon.

Retort Off-Gas

The retort off-gas carries oil and water generated in the retort to the oil recovery system where they are removed from the circulating gas stream.
  • Excess gas generated in the retort can be used as a fuel for internal process operations or to generate electricity.

Oil Recovery

The Oil Recovery System separates shale oil and water from the off-gas, now called recycled gas.
  • The oil and water collected in the oil recovery system are then separated by decanting.
  • The oil can be refined into a full range of petroleum products.


Oil Recovery System

Using components and process methods common to like industries, this system receives the off-gas from the Preheating and Mist Formation Zone of the Paraho® Retort. The principle functions of the oil recovery system are:

  • to separate condensable hydrocarbons and water from the off-gas;
  • to distribute the remaining non-condensable gas either as recycled gas to the retort or as product gas;
  • to supply air and/or recycled gas to the retort as required by Combination Mode operation.

Heat Recovery

As the hot, pyrolyzed shale gradually cools, it acts as a heat source to countercurrent flowing recycled gases used to heat unprocessed ore.
Paraho II™ Heating Zones

Paraho II™ Modes of Operation

The Paraho II™ process can be operated in three different heating modes, each with certain advantages and disadvantages:

Combustion Mode

Higher thermal efficiency , lower CAPEX and OPEX, and lower heating value product gas

Heated Mode

Higher heating value product gas, higher CAPEX and OPEX and lower thermal efficiency

Combination Mode

By balancing the heating methods of Combustion and Heated modes, the process can be further optimized to accommodate different shale characteristics.

Several factors determine the mode (or modes) of operation used for commercial scale applications:

  • Desired economic benefits
  • Oil shale characteristics
  • Operational parameters
  • Preferred product, co-products, and by-products

Characteristics Common to All Modes

All operating modes share common zones that perform common functions. Generally speaking, all modes of operation have four zones:

The Preheating and Mist Formation Zone

In the Preheating and Mist Formation Zone, screened shale is continuously fed into the top of the Paraho® Retort. Heat from the rising process gasses is transferred to the incoming shale. This zone acts as a countercurrent heat exchange, improving the overall efficiency of the process. As product gasses rise, the oil vapors condense into an aerosol mist. The mist-laden off-gas then is transferred to the oil recovery system.

The Pyrolysis Zone

Preheated shale then enters the Pyrolysis Zone where it is heated to between 450-500°C (842-932°F). As the organic matter in the oil shale – called kerogen – pyrolyzes, it yields oil vapors, other gasses and char. The oil vapors and gasses are swept upward into the preheating and mist formation zone, while the char remains on the retorted shale and descends downward into the heating zone.

The Heating Zone

The heating zone is where the energy for the overall retorting process is supplied. In the case of the Combustion Mode of operation, this energy is supplied by combusting the residual char that remains on the retorted shale. The oxygen required for the combustion reactions is supplied by adding air to the recycle gas that is injected into this retorting zone. In the case of the Heating Mode of operation, the required energy is supplied by injecting hot recycle gas that has been heated in externally fired heaters.

Within the Heating Zone are two sub-zones: the Primary Heating Zone and the Secondary Heating Zone. These sub-zones increase process flexibility by giving operators greater control over the temperatures within each of the processing zones. This added degree of temperature control, in turn, accommodates the means by which the process can be optimized to provide maximum oil yields and throughput rates.

The Cooling Zone

After leaving the Heating Zone, retorted shale enters the Cooling Zone. During this transition, heat from the retorted shale is transferred to the rising recycled gas, which represents a significant portion of the total gas flow through the retort. In addition to cooling the retorted shale for safe discharge from the system, this countercurrent heat exchange also improves the overall thermal efficiency of the process.

Synthetic Sweet Crude

Since the crude shale oil produced by the Paraho® process is thermally unstable, it requires some degree of refining in order to make it suitable for storage and transportation. This is typically done by hydro-treating the crude shale oil to remove sulfur and nitrogen and to stabilize the liquid hydrocarbon molecules. The result is synthetic crude suitable for refining into a variety of petroleum products.


A Paraho II™ shale oil plant may produce three major co-products:


The product gas, hydro-treated off-gas, and sour-water contain various levels of hydrogen sulfide that can, in turn, be processed into elemental sulfur or sulfuric acid.


Sour-water treatment can produce anhydrous ammonia.


Some modes of operation produce enough excess product gas to generate electricity in a gas-turbine or steam-turbine cogeneration system. The resulting electricity can be used to operate the plant, sell to a utilities grid, or both.


Depending on oil shale composition, the process of extracting oil from shale yields by-products like aromatic compounds, waxes, pitch, and asphalt. STIS’ R&D team continues to search for new and profitable by-products that enhance the economic value of shale oil extraction.

Paraho II™ Water Requirements


Paraho® Retort operation requires no water feed input. The free and mineral-bound water content of the raw shale, along with the water vapor produced by combustion can be captured, treated, and used in other areas, including dust control in the mining operation and retorted shale compaction.


Prior oil shale operations have demonstrated that retorted shale can be reclaimed in an environmentally acceptable manner. The mining method used to unearth shale helps determine how the retorted shale is reclaimed. In surface mining, retorted shale may be re-deposited into the mine void. For sub-surface mining, a permanent, above ground landfill may be created to hold the retorted shale. Once a retorted shale fill reaches capacity, overburden and top soil can be spread over the fill, and the surface contoured to resemble adjacent landscapes. Finally, the newly contoured surface can be vegetated with local flora to blend with natural surroundings.

Paraho II™ NIR Technology

Near Infrared (NIR) in Oil Shale Processing

How Can Oil Shale Processing Benefit From NIR Technology?

Real-Time Shale Grade Detection

Shale Tech International Services (STIS) has developed a robust production model that determines the grade of shale as it passes along a conveyor belt prior to being fed to the retort. Our model is capable of giving results within 1 gpt of a Fischer Assay (FA) system.

Real-Time Moisture Detection

Our production model is capable of determining the free moisture content of the shale before it enters the retort. This allows us the ability to adjust energy balances in the retort before any moisture related upsets occur.

Real-Time Yield Assessment

By utilizing the NIR, shale grade detection results and our Coriolis meters for real time oil make, STIS is able to calculate our production yield instantly, allowing us to make adjustments to the process as needed to ensure our production yields stay on target.

Shale Blending

A dynamic blending process can be developed by utilizing multiple NIR systems over several conveyors to blend shale online and achieve desired kerogen content.

Automatic Retort Functionality

STIS engineers are developing an automation loop that utilizes our online NIR results from shale grade and moisture to automatically adjust control variables within the retort.