Patent Application
20180291273
The invention relates to thermal conversion of solid fuels with a low organic content, e.g., oil shale, and can be used in the fuel-processing industry at production of a liquid or gaseous fuel, or an alternative fuel to substitute oil.
There is a known method and a plant for its implementation (Stelmakh G.N., Tyagunov B.N., et al. Electric process plant for conversion of fine-grained oil shale. Oil shale, No. 2/2, 1985, pp. 189-196).
The method comprises drying of ground fuel with a gaseous drying agent, pyrolysis of dried fuel with a solid heat-carrying agent with generation of vapour gases and coke-ash residue, burning the latter in a heated air flow with formation of gas suspension, staged separation of the gas suspension into an ash heat-carrying agent to be returned to the pyrolysis stage, ash to be fed to cooling and withdrawn from the process, and flue gases to be fed to after-burning and later used as a gaseous drying agent.
The plant for implementation of this method comprises, arranged in series, a flash-process drier, a waste drying agent separator, a pyrolysis reactor, its inlet connected to the fuel discharge branch pipe of the waste drying agent separator, a flash-process furnace, a solid drying agent separator, its dust discharge branch pipe connected to the reactor inlet, a drying agent separator, an ash cooler connected to the ash discharge branch pipe of the drying agent separator, and a recovery boiler, its inlet connected to the gas exhaust branch pipe of the drying agent separator, and its outlet connected to the flash-process drier.
The disadvantage of the method lies in that after-burning of flue gases in the recovery boiler at a α<1 results in incomplete oxidation of combustible components contained therein, and hence, to pollution of the environment with products of incomplete combustion of organic fuels. Pollution of the environment is also contributed to by the fact that, in the course of drying in the flash-process drier, some of the fuel particles are overheated, which results in bertinization products (carbon monoxide, hydrogen sulphide, carcinogenic substances, etc.) coming into the waste drying agent, thus polluting the environment.
There is also known a method and a plant for thermal conversion of oil shale (see RF patent No. 1766949, priority of Jun. 04, 1990, IPC C10B 53/06).
The method comprises drying of fuel with a gaseous drying agent, separating the fuel from the waste drying agent, pyrolysis of dried fuel with circulating solid heat-carrying agent with generation of vapour gases and coke-ash residue, burning the latter and formation of gas suspension, staged separation of the latter into a circulating heat-carrying agent to be returned to the pyrolysis stage, a gaseous drying agent to be fed to the drying stage, and an ash-and-smoke mixture, cooling this mixture and separating the same into ash to be withdrawn from the process and flue gases to be fed to the drying stage.
The plant for implementation of this method comprises, arranged in series, a flash-process drier, a waste drying agent separator, a pyrolysis reactor, its inlet connected to the fuel discharge branch pipe of the waste drying agent separator, a flash-process furnace, a solid drying agent separator, its gas exhaust branch pipe connected to the drier inlet, an ash-and-smoke mixture cooler and an ash separator, its gas exhaust branch pipe connected to the smoke exhauster and further to the flash-process drier.
The disadvantage of the method lies in that no after-burning is provided for flue gases of the flash-process furnace, which results in pollution of the environment with products of incomplete combustion.
The closest to the claimed invention are the method and plant for thermal conversion of high-ash fuels (see RF invention No. 2118970, priority of Apr. 25, 1997, IPC C10B 53/06, C10B 49/18).
The method is implemented as follows. The fuel is dried in a drier, then the fuel is separated from the waste drying agent in the separator and is pyrolyzed in a pyrolysis reactor. The generated coke ash residue is burnt in a flash-process furnace. The gas suspension obtained after burning is subjected to staged separation in separators into a solid heat-carrying agent, a gaseous drying agent and an ash-and-smoke mixture, which is cooled in a cooler and is separated in a separator into ash and flue gases. A part of the flue gases is recirculated to the stage of cooling the ash-and-smoke mixture, with the concentration of solid particles in this mixture maintained by adjusting the flow rate of recirculating flue gases. The remaining part of the flue gases is burnt in a recovery boiler along with the waste drying agent, with the temperature at the drying stage maintained by adjusting the flow rate of the flue gases being burnt.
The disadvantage of this method and plant is that to ensure regulating the quantity of the material being fed and the temperature it is necessary to install additional equipment, e.g., a heat exchanger, or a separator, which complicates the arrangement. Besides, delivering a part of ash at the temperature of 250-600° C. complicates handling the process, as it requires accuracy in feeding a loose material at a constant temperature: feeding a loose material at a temperature below 250° C. may result in termination of the burning process, while limiting the minimum ash temperature to 250° C. would result in larger amounts of the material fed and, as a consequence, a larger volume of the furnace combustion chamber, as well as larger dimensions of equipment for separation of the heat-carrying agent and ash.
The objective of the proposed invention is to ensure temperature control in the flash-process furnace and to reduce the overall dimensions and metal consumption of equipment.
The method for conversion of oil shale or high-ash solid fuels comprises flue-gas drying of feedstock, recovering the solid phase as a heat-carrying agent, feedstock pyrolysis in a reactor, separating a gas-vapour mixture from the coke-ash residue in a dust-settling chamber, discharging ash, cooling flue gases, and combustion of the coke-ash residue. Here, an inert material having an ambient temperature is supplied to the outlet of the coke-ash residue ignition chamber for temperature control in the flash-process furnace, and ash from the ash discharge system with a temperature of 10 to 200° C. is used as an inert material.
The plant for implementation of this method comprises, arranged in series, flash-process drier 1, waste drying agent separator 2, pyrolysis reactor 3, its inlet connected to fuel discharge branch pipe of the waste drying agent separator, flash-process furnace 5, solid drying agent separator 6, its gas exhaust branch pipe 7 connected to the drier inlet, ash-and-smoke mixture cooler 8 and ash separator, its gas exhaust branch pipe connected to the smoke exhauster and further to the flash-process drier. The plant operates as follows.
The shale ground to 0-25 mm is fed with an auger to flash-process drier 1, where the shale is dried with exhaust flue gases. Next, the gas suspension of shale and the flue gases is fed to the dry shale cyclone for separation of the solid phase. Upon being mixed with the circulating ash heat-carrying agent, the dry shale is fed to reactor 3, where pyrolysis of the organic part of the shale occurs at temperatures 450-550° C. The pyrolysis products in the vapour phase and the mixture of the circulating heat-carrying agent with the mineral part of the shale are fed to dust-settling chamber 4. The vapours of pyrolysis products are fed to condensation (not shown in the diagram), where purification, fractionation, and cooling take place, and the target products are released (shale oil and pyrolysis gas).
The mixture of the circulating heat-carrying agent with the mineral part of the shale (coke-ash residue) from dust-settling chamber 4 is fed with an auger to flash-process furnace 5. Air is fed to the lower part of the flash-process furnace to ensure burning of organic matter in the coke-ash residue and to enable the flash drying process.
The gas suspension of combustion products, nitrogen and the solid phase is fed from the upper part of the flash-process furnace to the heat-carrying agent separator, wherefrom a part of the solid phase is returned to reactor 3. Further on, the gas suspension from the separator comes into ash cyclone 6, where it is separated into ash and flue gas. The flue gas is fed to heat recovery (recovery boilers) and into flash-process drier 1, where it gives heat to the shale drying process and further, after cyclone 2, is discharged through a filtration system into the atmosphere.
The ash from cyclone 6 is cooled down in an ash heat exchanger to the temperature of ˜80-120° C., and is then fed to humidification and further on to recovery. As distinct from the prototype, a part of the ash, prior to its humidification, is fed at the temperature 80-120° C. with an auger to the flash-process furnace to the outlet from the accelerating section of the furnace. Here, the coke-ash residue from the dust-settling chamber has been ignited, and delivering the ash enables to regulate the temperature in the furnace. Feeding “cold” ash at the temperature of 80-250° C. makes possible to increase the air flow to ensure the fluid dynamics of the spouted bed and to increase the air/combustibles ratio above 1, which ensures more thorough combustion of fuel in the coke-ash residue.
Therefore, the invention allows for a more complete use of the oil shale energy potential and for obtaining ash with a reduced negative effect on the environment, which makes it possible to use the ash for recultivation of quarries resulting from oil shale mining.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015153090 | Dec 2015 | RU | national |
This Application is a Continuation application of International Application PCT/RU2016/000793, filed on Nov. 30, 2016, which in turn claims priority to Russian Patent Applications No. RU2015153090, filed Dec. 10, 2015, both of which are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/RU2016/000793 | Nov 2016 | US |
| Child | 16004636 | US |
