AN IMPROVED CONFIGURATION OF METHOD AND APPARATUS FOR RECOVERING OIL FROM SOLID HYDROCARBONACEOUS MATERIAL

Abstract: A method of recovering oil from solid hydrocarbo­ naceous material such as oil shale using a dense phase fluidized bed in a retort (20) from which spent shale is withdrawn via a line (30) and burnt in a transport combustor (29) to heat the spent shale which is passed to a surge bed in a retort (24) from where it is passed through a control valve (44) back to the retort and used to heat raw feed shale from a feed line (21). Surplus heat medium particles are withdrawn from the surge bed (24) and passed to a second transport combustor (101) where they are burnt to give off heat for the generation of stream in pipes or coils (105) in the second transport combustor (101).

Description: AN IMPROVED CONFIGURATION OF METHOD AND APPARATUS FOR RECOVERING OIL FROM SOLID HYDROCARBONACEOUS MATERIAL This invention relates to an improved configuration of method and apparatus for recovering oil from solid hydrocarbonaceous material and has been devised particularly though not solely for the utilisation of the excess residual carbon in oil shale after the extraction of oil vapours. Many processes have been proposed for the recovery of oil from solid hydrocarbonaceous material such as oil shale or coal, but many of these methods are not suitable due to the low utilisation of energy and therefore the high cost of extracting the oil. One form of oil recovery from solid hydrocarbonaceous material is described in our co-pending Australian Patent Application 20678/83 where with reference to Figure 2 it can be seen that an attempt has been made to recover the maximum amount of energy by the incorporation of steam coils 36 into the transport combustor 29. Incorporation of such coils increases the pressure drop in the transport combustor requiring a high capacity air blower 31 which increases the capital expense and the operating cost of the plant. Furthermore the burning of substantially all of the residual carbon in the oil shale in the transport combustor 29 to achieve a high plant efficiency, results in problems of control of heating the heat medium shale to the required temperature for the reaction in the retort 20. It is therefore an object of the present invention to provide a method of and apparatus for recovering'oil from solid hydrocarbonaceous material which is inherently efficient and which will obviate or minimise the foregoing disadvantages in a simple yet effective manner, or which will at least provide the public with a useful choice. Accordingly in one aspect the invention may broadly be said to consist in a method of recovering oil from solid hydrocarbonaceous material comprising the steps of: contacting fresh feed hydrocarbonaceous material particles with heat medium particles in a dense phase fluidised bed, with the fliiiG sing medium for the bed being generated within the bed ar=ç* being constituted at least primarily by fluid released by conversion of kerogen in the feed material, withdrawing from the bed oil vapour which is produced as a result of heat exchange between the heat medium particles and the feed particles, progressively withdrawing the heat medium particles and spent feed material particles from the fluidised bed, heating the heat medium particles in a heating region external of the fluidised bed by burning residual carbon therein at a controlled rate sufficient to provide the heat needed for the said heat exchange, recirculating the necessary volume of heated particles through the fluidising bed with fresh feed material particles, withdrawing heat medium particles which are surplus to the said necessary volume of heated particles, and reheating the withdrawn heat medium particles by burning the residual carbon therein to provide additional usable heat. Preferably the additional usable heat is used to generate steam for use in the oil recovery process or in other processes. Preferably the withdrawn heat medium particles are reheated in a transport combustor by providing the required volume of air under pressure Preferably the transport combustor incorporates steam generation pipes or coils. In a further aspect the invention may broadly be said to consist in apparatus for recovering shale oil from oil shale. said apparatus comprising a retort adapted to contain a dense phase fluidised bed, a combustor arranged to receive spent feed shale and recirculating heat medium shale from said retort and to combust a portion of the residual carbon therein in the presence of a combustion supporting gas at a controlled rate. flow control means arranged to return controlled amounts of recirculated heat medium shale from said combustor to said retort, feed means adapted to feed fresh feed shale particles into said retort, extraction means adapted to extract shale oil vapour from said retort, and secondary combustion means arranged to receive the heat medium shale not returned to the retort, and to combust the remaining residual carbon thereon to provide additional usable heat. Preferably the secondary combustion means comprise a transport combustor provided with air under pressure at a sufficient rate to combust the remaining residual carbon. Preferably said'transport combustor incorporates pipes or coils for the generation of steam. In a still further aspect the invention may broadly be said to consist in apparatus for utilising excess residual carbon remaining in solid hydrocarbonaceous material after oil vapour recovery therefrom, said apparatus comprising a transport combustor to which the solid hydrocarbonaceous material is fed, air supply means arranged to supply air to the combustor to burn the residual carbon in the solid hydrocarbonaceous material, and steam generation means within the transport combustor. Notwithstanding any other forms that may fall within its scope, one preferred form of the invention will now be described by way of example only with reference to the accompanying drawing which is a schematic representation of a shale oil recovery plant incorporating the features of the present invention. The shale oil recovery plant shown in the accompanying drawing is a modification of the shale oil recovery plant described and illustrated with reference to Figure 2 of our co-pending Australian Patent Application 20678/83, The shale oil recovery plant comprises a retort 20 into which fresh particulate feed shale is delivered, by way of a feed line 21 from a surge bed 22 controlled by an inlet valve 43. Recirculating heat medium shale is also delivered to the retort 20 at a controlled rate, the heat medium shale being supplied by a feed line 23 and a control valve 44 from a dense phase fluidised surge bed which is contained within a vessel 24. The heat medium shale is delivered to the retort 20 in sufficient quantity to effect the retort temperature and holding time conditions sufficient to convert the kerogen content of the fed shale into gas and oil vapour products which are release at all levels throughout the bed of particulate matrial within the retort 20 and thus a fluidised bed is created without there being the need to inject a fluidising medium from an external source. Gas and oil vapour which migralzs above the fluidised bed in the retort 20 is drawn from t ie retort by way of a cyclone separator 25 and is delivered to a product fractionating system (not shown) by lay of a feed line 47 for subsequent processing to final cl transportable products. Spent feed shale and recirculating heat medium shale progressively passes from the fluidiid bed within the retort 20 and enters a stripping vessel 26 by way of a feed line 27 incorporating a control valve 45. Residual gas and oil vapour which is entrained in the')articles progress into the stripping vessel 26, are strippeitfrom the particles by gas or steam which is injected into -te stripping vessel, and the resulting gas and oil vapour± are directed into an upper region of the retort 20 by waysf a delivery line 28. The stripped spent shale and reirculating heat medium shale are thereafter passed from the stripping vessel 26 to a dilute phase transport combustor 2 by way of a valved feed line 30. The transport combustor 29 is constituted by a dilute phase burner into which the recirculated heat medium and spent feed shale is directed and in which residual carbon on or in the spent shale is burned in the presence of combustion supporting air. Thus, in contrast with the dense phase fluidised bed which is established within the retort 20, the transport combustor 29 functions as a dilute phase device into which fluidising air is directed by a blower 31. Air from the blower 31 is admitted to the lower region of the transport combustor 29 by way of a controlled delivery line 32 and the air entrains the spent feed shale and the recirculating heat medium shale from the stripping vessel and carries the shale particles along the length of the transport combustor 29. During the particle residence time in combustor 29, the residual carbon on and in the shale is burnt in the presence of the entraining air, and the heat of combustion raises the temperature of the particles to the level required to effect the fluidised bed retorting in the retort 20. When the spent shale particles enter the transport combustor and are elevated in temperature, such particles may be regarded as being recirculating heat medium shale because they are thereafter directed, at an elevated temperature, into the surge bed vessel 24 and into the retort 20 together with previously recirculated heat medium shale. Having passed through the transport combustor 29 the recirculating heat medium particles and the entrained gas are delivered to a cyclone 33 which functions to separate the solid particles from the gas. The entraining gas and air which exits from the surge bed 24 is expelled as flue gas and the solid particles are directed into the surge bed 24 for subsequent transfer into the retort vessel 20. The surge bed 24 is conveniently fluidised by way of air from the blower 31 via the controlled air inlet line 35. Obviously as fresh feed shale is fed into the system from the surge bed 24 it is necessary to withdraw the excess recirculating heat medium shale to maintain a constant level 5f particles within the process. The excess heat medium shale is withdrawn via a delivery line 34 from the surge bed 24 controlled by control valve 100. The excess heat medium shale is then delivered to the lower end of a transport combustor 101 which is provided with air through air supply line 102 from a low pressure air blower 103 controlled by control valve 104. The transport combustor 101 is similar in operation to the combustor 29 described above but incorporates steam generation pipes or coils 105. The remaining residual carbon in the shale delivered to the transport combustor 101 is combusted by the air delivered through the line 102 giving off further heat to generate steam within the pipes or coils 105. The steam pipes or coils 105 are connected in circuit with a source 37 of water and function to generate steam for use in the oil recovery plant or in associated equipment. By way of contrast with the plant described with reference to Figure 2 of our co-pending Australian Patent Application 20678/83 the steam is generated in a separate transport combustor 101 rather than by way of steam generation pipes or coils incorporated in the main transport combustor 29. The control of the primary combustor 29 is simplified by not having to also control the amount of steam generated therein. As the carbon residue percentage on solids is higher, reaction rates and utilisation of combustion air are both improved. There is little requirement for excess air to accomplish the desired heating of the heat medium shale and this helps to make control in the transport combustor 29 more precise. The heat of the recirculated heat medium shale issuing from the transport combustor 29 may be accurately controlled by controlling the amount of residual carbon burnt by the control of the air from the blower 31. As only a portion of the residual carbon is burnt in the transport combustor 29 a lower capacity air blower may be utilised compared with that shown in our earlier patent application with a consequent saving in both capital and operating costs. The hot spent shale from the circulating shale surge vessel 24 flows down a dense phase stand pipe 34 through a throttling control valve 100 to enter the dilute phase combustion riser 101. Combustion air enters the same riser at a level slightly below the solids entry, carrying them up in a dilute phase flow while burning the remaining residual carbon within the shale to release heat. This heat is radiated to the steam tubes 1Q5 positioned on the riser walls generating steam for use elsewhere. The combustion air amount may be accurately controlled to match the amount of carbon available in the shale or, alternatively, the amount of steam which the plant can profitably utilise. Gas velocity in the riser 101 may reasonably vary over a range of about 15 to 75 feet per second allowing good flexibility in the amount of carbon that can be burnt. Flue gas and shale solids are separated in cyclones (not shown) at the top of the riser. In this manner a plant for the extraction of oil vapour from solid hydrocarbonaceous material may be provided with the following advantages. Burning only part of the available carbon residue in the primary combustor 29 improves the oxygen-carbon reaction rate and lowers or essentially eliminates the amount of unreacted, 11excess", oxygen in the exit flue gas streams. Removing the steam generation surface and heat load from the primary combustor simplifies control of the circulating shale temperature. The amount of air injected into the combustor directly sets the outlet temperature and this can be readily adjusted as needed. There is no conflicting requirement to also control the amount of heat used to generate steam. If steam is generated in the primary combustor. control of that heat absorbtion must be by the amount of steam tube surface provided and by the operating pressure and temperature of the steam boiler system. Each of these controls is mainly determined by the original plant design and allows relatively little flexibility in operation. The result finally is that control of hot circulating solids temperatures and the required flow rates to the retort will be less stable and can adversely affect product yield and properties. Burning the remaining carbon residue in a secondary combustor is conducted only for the purpose of recovering the carbon fuel values to the extent that this is economically feasible. The a3vtount of carbon burnt is directly related to the amount of oxygen (air) injected. Regulation of this flow provides a single and effective variable for control of the combustor. If carbon removal of a very low level is required, say 0,05 weight percent on discarded shale, an appreciable amount of excess oxygen may be present in the flue gas from the secondary combustor 101. A typical range might be 0.5 to 3 percent. If both process heat and steam generation heat are provided by the same combustor, then a comparable percentage of excess air will be required for the total air supply. Depending upon specific plant requirements, having separate primary and secondary combustors permits a lower operating pressure for a substantial part of the combustion air and a consequent saving in compression horse power. The investment and operating costs for air compressors and related apparatus is a significant factor for shale plants employing residual carbon combustion.

Claims: CLAIMS: 1. A method of recovering oil from solid hydrocarbonaceous material comprising the steps of: contacting fresh feed hydrocarbonaceous material particles with heat medium particles in a dense phase fluidised bed (20), with the fluidising medium for the bed being generated within the bed and being constituted at least primarily by fluid released by conversion of kerogen in the feed material. withdrawing from the bed oil vapour which is produced as a result of heat exchange between the heat medium particles and the feed particles, progressively withdrawing the heat meaium particles and spent feed material particles from the fluidised bed, heating the heat medium particles in a heating region (29) external of the fluidised bed by burning residual carbon therein at a controlled rate sufficient to provide the heat needed for the said heat exchange, recirculating the necessary volume of heated particles through the fluidising bed with fresh feed material particles, characterised by the steps of: withdrawing heat medium particles which are surplus to the said necessary volume of heated particles, and reheating the withdrawn heat medium particles by burning the residual carbon therein to provide additional usable heat. 2. A method as claimed in claim 1 wherein the additional usable heat is used to generatewsteam for use in the oil recovery process or in other processes. 3. A method as claimed in claim 1 wherein the withdrawn heat medium particles are reheated in a transport combustor (101) by providing therequired volume of air under pressure. 4. A method as claimed in claim 3 wherein the transport combustor incorporates steam generation pipes or coils (105). 5. Apparatus for recovering shale oil from oil shale, said apparatus comprising a retort (20) adapted to contain a dense phase fluidised bed, a combustor (29) arranged to receive spent feed shale and recirculating heat medium shale from said retort and to combust a portion of the residual carbon therein in the presence of a combustion supporting gas at a controlled rate. flow control means (24) arranged to return controlled amounts of recirculated heat medium shale from said combustor t said retort, feed means (23) adapted to feed fresh feed shale particles into said retort, and extraction means (25) adapted to extract shale oil vapour from said retort, characterised by the provision of secondary combustion means (101) arranged to receive the heat medium shale not returned to the retort, and to combust the remaining residual carbon thereon to provide additional usable heat. 6. Apparatus as claimed in claim 5 wherein the secondary combustion means comprise a transport combustor (101) provided with air under pressure at a sufficient rate to combust the remaining residual carbon. 7. Apparatus as claimed in claim 6 wherein said transport combustor incorporates pipes or coils (105) for the generation of steam. 8. Apparatus for utilising excess residual carbon remaining in solid hydrocarbonaceous material after oil vapour recovery therefrom, characterised by the provision of a transport combustor (101) to which the solid hydrocarbonaceous material is fed, air supply means (102) arranged to supply air to the combustor to burn the residual carbon in the solid hydrocarbonaceous material, and steam generation means (105) within the transport combustor.

Inventors: DANIELS, LUDLOW SULLIVAN
Applicants: AUSTSHALE N.V., DANIELS, LUDLOW
Application year: 1985
Main classification: C10G1
IPC codes: C10G1