Method for burning petroleum coke gasification slag in a multistage fluidization device

Abstract

The application discloses a combustion method of petroleum coke gasification slag in a multilayer fluidization device, which is mainly composed of a double-layer fluidized bed, a cyclone burner and a fine powder burner and the like in connection. The petroleum coke POX slag has problems of difficult ignition due to less volatile content, low heat value, difficult stable combustion, fast / slow combustion stages, high fine slag content and the like. In view of the above difficulties, a petroleum coke POX waste slag carbon reduction process is provided, which has the advantages that the fluidized combustion mode improves the mass transfer and heat transfer rate; the staged combustion avoids the back mixing of particles; the gas-solid reverse operation can effectively utilize heat energy. The reaction device theme includes a double-layer fluidized bed, a cyclone burner at the top of the reactor and a fine powder burner at the lower layer feed inlet of the reactor. The material enters the fluidized bed from the upper layer for combustion, part of the bed material enters the lower layer fluidized bed for continuous combustion, and is discharged after reaching the standard; the fine particles are further combusted in the cyclone burner at the top of the reactor; the out-of-furnace fly ash is combusted in the fine powder burner, the product enters the lower layer bed, and the cycle is completed.

Description

Technical Field

[0001] This invention belongs to the fields of petrochemicals and environmental protection, and is specifically applied to the treatment of petroleum coke gasification waste residue (i.e., petroleum coke POX residue). It provides a method for combustion of petroleum coke gasification residue in a multi-layer fluidized bed. Background Technology

[0002] Currently, high-sulfur petroleum coke cannot leave the factory without processing. Refinery petroleum coke-to-hydrogen (POX) units are forced to use more high-sulfur and high-heavy-metal-content petroleum coke as feedstock to gasify hydrogen. The ash residue produced after petroleum coke hydrogen production still contains some residual carbon, requiring carbon reduction and possessing waste heat recovery value, but it differs from conventional coal and other solid fuels. The differences lie in the low carbon content of POX ash residue, generally around 20% to 40%, ultra-low volatile matter, high fine powder content, and low calorific value (1000 to 2000 kcal / kg). These characteristics necessitate burner design to overcome difficulties in ignition and stable combustion, as well as long combustion times. Simultaneously, the subsequent removal of heavy metals from residual ash must be considered, and excessively high combustion temperatures that could lead to the formation of glassy slag, thus increasing the difficulty of heavy metal recovery, should be avoided.

[0003] CN 1959207 A discloses a petroleum coke / petroleum coke gasification slag combustion treatment device. The device mainly consists of an upper and lower reactor. Material from the lower stage enters the upper stage through an inner riser pipe to continue the reaction, while material from the upper stage enters the lower stage through inner and outer overflow pipes, thus achieving long-term circulation and residence of the material within the reactor. The lower burner distribution plate is equipped with a guide tube, dividing the lower burner into two combustion zones. The gas velocity inside the guide tube is 0.15 m / s, the gas velocity outside the guide tube is 0.6 ~ 1.8 m / s, and the gas velocity in the inner riser pipe is 6 ~ 12 m / s. Combustion auxiliary air enters the burner from the upper / lower stage distribution pipes / plates. Further, the lower stage flue gas enters the upper burner along with the material through the inner riser pipe, and then exits the burner through a cyclone at the top of the upper burner. The upper and lower stages each have feed inlets, and the material particle size is 0 ~ 1000 μm.

[0004] CN 101666489 A discloses a petroleum coke slurry combustion device. It includes a heat storage chamber within a furnace and a fuel oil / gas combustion nozzle connected to the heat storage chamber and mounted on the furnace wall. Outside the fuel oil / gas combustion nozzle, from the inside out, are sequentially fitted a petroleum coke slurry atomizing nozzle, an inner combustion air nozzle, and an outer combustion air nozzle, all connected to the heat storage chamber. An inner combustion air swirl generator and an outer combustion air swirl generator are respectively installed inside the inner and outer combustion air nozzles.

[0005] CN 105627294 A discloses a petroleum coke combustion device, mainly comprising an upright cylindrical furnace shell with collinear central axes, a cylindrical furnace liner, grate bars, and an air inlet pipe. The bottom edge of the furnace liner is welded to the bottom plate of the furnace shell. The width of the annular cylindrical region between the furnace liner and the furnace shell is 0.41 to 0.43 times the radius of the furnace liner. The grate bars move up and down seamlessly against the furnace liner. Coke particles are piled above the grate bars, and the combustion chamber is located above the coke particle layer. The annular cylindrical region between the furnace liner and the furnace shell, and the cylindrical region of the furnace liner are connected by numerous connecting ports at the bottom of the furnace liner. After the connecting region is filled with pure water, it forms a communicating vessel between the outer and inner cylindrical regions. The height of the water column in the outer annular region above the top surface of the coke particle layer is equal to the thickness of the coke particle layer in the inner cylinder. This invention can be used in furnaces burning low-sulfur petroleum coke particles. The invention has an energy saving rate of >5% to 15%.

[0006] CN 201983260 U discloses a utility model relating to a petroleum coke powder cyclone combustion device, including a petroleum coke powder burner, a control system, and a high-temperature pulse ignition cap disposed on the nozzle and communicating with the combustion chamber. A pulse action channel communicating with the interior of the petroleum coke powder burner is provided on the high-temperature pulse ignition cap. A pulse generation system communicating with the interior of the high-temperature pulse ignition cap is provided within the pulse action channel. The pulse action channel is also connected to ignition liquefied gas. The atomizing gas system, the primary powder injection channel, the pulse generation system, and the ignition liquefied gas are all connected to the control system. The device employs premixing and semi-premixing technologies for petroleum coke powder and combustion air, as well as cyclone combustion control technology. The use of flame holes on the high-temperature pulse ignition cap allows for the adaptation to different specifications of petroleum coke powder particles.

[0007] CN 202709086 U discloses a novel coal ash powder combustion device for power plant boilers, including a power plant boiler furnace and a cyclone combustion tube connected to the boiler furnace. The cyclone combustion tube is installed at the front and rear of the boiler furnace. A spray gun is provided above the cyclone combustion tube to spray coal ash powder into the combustion chamber of the cyclone combustion tube at high speed. A primary rotating air supply port is provided at the top of the cyclone combustion tube to supply the air required for ignition of the coal ash powder. A secondary tangential air supply port is provided at the upper part of the cyclone combustion tube to supply the air required for complete combustion of the coal ash powder.

[0008] CN 206377652 U discloses a petroleum coke particle combustion device with dust filtration function, including an outer furnace wall and an inner furnace wall, with a closed cavity formed between the outer and inner furnace walls, and the closed cavity is filled with cooling water. A combustion chamber is provided inside the inner furnace wall, with grate bars at the bottom of the combustion chamber. A furnace air inlet pipe is vertically connected to the lower side of the grate bars, and an induced draft fan is connected to the other end of the furnace air inlet pipe. An end cap is connected to the top of the outer furnace wall, and a flue gas passage is provided on the end cap. An elliptical head is connected to the top surface of the end cap, and a filter box is provided inside the elliptical head. One end of the flue gas passage passes through the end cap and communicates with the combustion chamber, while the other end of the flue gas passage is connected to the filter box. The outlet end of the filter box passes through the elliptical head, and the filter box is equipped with a filter screen. Multiple water atomizing nozzles are fixedly arranged circumferentially along the inner wall of the filter box below the filter screen. A sewage discharge channel is connected to the bottom of the filter box.

[0009] POX slag, produced from petroleum coke, contains a small amount of carbon, with a carbon content mostly between 20% and 40%. Some patents mention using circulating fluidized beds for processing coal gangue. Other patents mention composite fluidized combustion devices for treating gasified coal slag and biomass fuel. However, due to the unique characteristics of petroleum coke POX slag, such as low calorific value, difficult ignition, poor reactivity, staged reaction process, and wide particle size distribution, there is currently no mature carbon reduction and chemical heat recovery process. Furthermore, the issue of recovering heavy metals from the petroleum coke POX slag after combustion must also be considered. Summary of the Invention

[0010] The purpose of this invention is to provide a multi-layer fluidized bed petroleum coke (POX) waste combustion method, which mainly consists of a double-layer burner, a swirl burner, and a fine powder burner connected to form a reaction unit. The basic principles of this design are: firstly, the combustion rate of petroleum coke (POX) waste is significantly slower than that of coal gangue, requiring a residence time on the order of hours; secondly, there are significant differences in reaction rate at different stages of the combustion process of petroleum coke (POX) waste, with the combustion rate gradually slowing down as the combustion reaction progresses; and thirdly, given the wide particle size distribution and high fine content of petroleum coke (POX) waste, the goal is to ensure the fine slag is burned as completely as possible while minimizing ineffective particle recycling. Its advantages are as follows: First, the use of fluidized bed combustion can improve the overall mass transfer, heat transfer, and combustion rate of the reaction, overcoming the problem of low ignition point of POX slag; second, staged combustion can effectively avoid backmixing of solid particles during the reaction, improving the reactor's processing efficiency; during staged combustion, the combustion air and material achieve countercurrent heat exchange, maximizing the utilization of the calorific value in petroleum coke POX slag; finally, the cyclone burner and fine powder combustion device can effectively handle fine powder and reduce ineffective particle circulation. The double-layer burner is designed with a combination of upper and lower fluidized beds separated by a distribution plate. The material first enters the upper fluidized bed for combustion. The upper and lower fluidized beds are connected by internal / external overflow pipes. Unburned material in the upper bed is further burned in the lower fluidized bed, and fine particles carried by the airflow into the cyclone at the top of the upper fluidized bed are further burned by the cyclone combustion device, further improving the overall carbon conversion rate. The ultrafine fly ash is collected by a cyclone outside the reactor and then burned in an oxygen-enriched fine powder burner connected to the lower fluidized bed. The high-temperature flue gas and residue after combustion enter the lower reactor. Combustion air enters the reactor through cyclone burners at the bottom and top of the double-layer bed, respectively. The flue gas is discharged uniformly from the upper part of the double-layer fluidized bed into the subsequent purification unit. Water-cooled heat exchange devices are installed on the walls of both double-layer beds to control the burner reaction temperature.

[0011] To achieve the above objectives, petroleum coke (POX) residue with a particle size range of 0-1 mm, after initial treatment, enters the upper layer of the double-layer burner from the silo, where it is rapidly heated to over 600 °C for combustion. The material in the upper fluidized bed is controlled to flow into the lower fluidized bed via internal / external overflow pipes for further reaction. The reaction temperature in the lower fluidized bed is controlled between 600 °C and 1000 °C until the carbon conversion rate reaches 95%, at which point it is discharged from the lower fluidized bed. The double-layer burner is divided into two layers by a central distribution plate. Combustion air is supplied to the reactor from two points: one under the lower air distribution plate and the other under the upper air distribution plate. The air inlet ratio at the two air inlets varies between 0:1 and 3:1. The air inlet volume of the top swirl combustion device does not exceed 20% of the total air inlet volume of the combustion unit. The oxygen concentration in the air supplied to the fine powder burner can be as high as 100%.

[0012] Furthermore, the dual-layer burner can have upper and lower beds of equal diameter, with an enlarged section connected above the upper fluidized bed, and the ratio of the enlarged section to the combustion section is between 1:1 and 3:1. The upper and lower layers of the combustion reactor can have unequal diameters, specifically with the ratio of the lower to upper section diameter varying between 1:1 and 1:2.

[0013] Furthermore, the reaction device can be a double-layer burner operating as a whole, or a multi-layer burner operating. In the case of multiple layers, each layer is provided with a feed port and an overflow port to overflow bed material to the lower layer.

[0014] Furthermore, the materials fed into the system include, but are not limited to, petroleum coke (POX) waste residue, or a mixture of petroleum coke (POX) slag and other carbon-containing solid fuels such as coal / petroleum coke / biomass, or ash slag or inert materials added to the system as heat carriers for circulation.

[0015] Furthermore, the operating gas velocity in the lower layer of the dual-layer burner is 0.3 ~ 1 m / s, and the operating gas velocity in the upper layer of the dual-layer burner is between 0.7 ~ 1.8 m / s.

[0016] Furthermore, the multi-layer fluidized bed combustion method can use air as the combustion air, or it can use oxygen-enriched air or pure oxygen as the combustion air for operation. Each air inlet of the dual-layer burner can be selected as air / oxygen-enriched air / pure oxygen as the combustion air. The air inlets include, but are not limited to, distribution plates, distribution pipes, etc.

[0017] The beneficial effects that can be obtained from this invention are:

[0018] The method provided by this invention reduces the low reactor efficiency caused by using a single fluidized bed or circulating fluidized bed device in the combustion of petroleum coke POX slag through the organic combination of reactors, and also further improves the processing flexibility of the reaction system.

[0019] The method provided by this invention effectively distributes the heat of the system through multi-stage operation, stabilizing combustion. For example, excess air in the lower part of the double-layer bed can be preheated by the lower fluidized bed, thereby accelerating or stabilizing the combustion effect of the upper fluidized bed.

[0020] The method provided by this invention further improves the overall carbon conversion rate by using a swirling combustion or fine powder oxygen-enriched combustion device for ultrafine particles, and effectively recovers the residual chemical energy of ultrafine particles in petroleum coke POX residue.

[0021] The method provided by this invention can control the oxidation state of metals in POX ash by controlling combustion at different stages, thereby helping to recover heavy metals. Attached Figure Description

[0022] AppendixFigure 1 This is a flowchart of the POX waste incineration method.

[0023] The numbers in the attached diagram are explained as follows:

[0024] 1. Feed hopper; 2. Upper section of double-layer burner; 3. Lower section of double-layer burner; 4. Swirl burner; 5. Inner overflow pipe; 6. Outer overflow pipe; 7. Flue gas outlet; 8. Fine powder burner; 9. Heat exchanger; 10. Cyclone separator; 11. Reactor expansion section. Detailed Implementation

[0025] This invention provides a fluidized bed combustion reaction method for petroleum coke (POX) waste residue, which is further described below with reference to the accompanying drawings.

[0026] Inside the silo (1), 0-1 mm petroleum coke POX residue enters the upper section (2) of the double-layer burner from the feeder and rapidly mixes and heats up with the existing bed material. The raw material petroleum coke POX residue heats up rapidly and begins to burn. The operating gas velocity of the upper fluidized bed is controlled at 0.7-1.8 m / s, and the reaction temperature of the upper section is between 600-1000 ℃. Part of the bed material in the upper section (2) of the double-layer burner enters the lower layer (3) of the burner through the external overflow pipe (6) or the internal overflow pipe (5) to continue combustion. The overflow rate of the external overflow pipe is controlled by the slide valve on the overflow pipeline, and the overflow rate of the internal overflow pipe is controlled by the pressure drop between the bed layers. The internal and external overflow pipes work together. When the carbon conversion rate reaches the standard, it is discharged from the lower burner (3). Some fine particles in the upper fluidized bed enter the upper cyclone burner (4) of the multi-layer bed with the flue gas to continue the combustion reaction. The flue gas leaves the burner through the cyclone separator (10) outside the reactor and enters the purification and separation unit for discharge. The collected fly ash particles are rapidly combusted by a fine powder burner (8), with the temperature controlled between 600 ℃ and 1000 ℃. The combustion exhaust gas enters the lower section of the double-layer burner to supplement the heat of the lower bed. Combustion air enters the reactor from the lower air distribution plate, upper air distribution plate, swirl burner inlet, and fine powder burner inlet of the multi-layer burner for combustion support. Heat is extracted through heat exchangers (9) arranged on the walls of the double-layer burner, while the furnace temperature is controlled within the normal range.

Claims

1. A fluidized combustion method of petroleum coke POX residue, characterized in that: (1) fast carbon combustion stage: first, the treated petroleum coke POX residue with a particle size range of 0-1 mm is fed from the stock bin into the upper layer of the double-layer combustor, and is rapidly heated to above 600 DEG C for combustion reaction; (2) residual carbon combustion stage: the material in the upper section of the double-layer combustor enters the lower layer of the combustor for continuous combustion through the outer overflow pipe or the inner overflow pipe, the overflow amount of the outer overflow pipe is controlled by the slide valve on the overflow pipe line, and the overflow amount of the inner overflow pipe is controlled by the pressure drop between the bed layers, and when the carbon conversion rate reaches the standard of 95%, the material is discharged from the lower combustor; (3) combustion treatment of fly ash carbon: through the organic combination of the double-layer combustor, the cyclone combustor and the fine powder combustor, the residual carbon in the petroleum coke POX residue can be effectively treated to achieve the purpose of carbon reduction and chemical heat, the fly ash particles passing through the cyclone separator are rapidly combusted through the fine powder combustor, the temperature is controlled between 600 DEG C and 1000 DEG C, and the combustion tail gas enters the lower section of the double-layer combustor to heat the lower bed layer; (4) combustion air distribution: the double-layer combustor is separated by the middle distribution plate, the upper layer and the lower layer of the fluidized bed are both provided with air distribution plates, the combustion air is fed into the reactor from the two air inlet points of the lower air distribution plate or the upper air distribution plate, the air inlet amount of the two air inlet points of the upper layer and the lower layer of the fluidized bed varies between 0:1 and 3:1, the air inlet amount of the cyclone combustor at the top of the fluidized bed is not more than 20% of the total air inlet amount of the whole unit, and the air distribution oxygen concentration of the fine powder combustor is 100%; (5) heat recovery: the reaction temperature is controlled by the water-cooled wall device arranged on the double-layer combustor, and additional energy is recovered. The double-layer combustor is of equal diameter or unequal diameter between the upper bed layer and the lower bed layer, and if it is of unequal diameter, the specific diameter ratio of the upper section to the lower section varies between 1:1 and 2:

1. The operating gas speed in the lower layer of the double-layer combustor is 0.3-1 m / s, and the operating gas speed in the upper layer of the double-layer combustor is 0.7-1.8 m / s. The petroleum coke POX residue is the gasification ash residue obtained after gasification of petroleum coke, or a mixture of the gasification ash residue obtained after gasification of petroleum coke, coal, petroleum coke and biomass. The fluidized combustion method uses air, oxygen-enriched air or pure oxygen as the combustion air for operation, and air, oxygen-enriched air or pure oxygen is selected as the combustion air at each air inlet point of the double-layer combustor. ​ 2. The method of claim 1, wherein: ​ 3. The method of claim 1, wherein: ​ 4. The method of claim 1, wherein: ​ 5. The method of claim 1, wherein: ​

Images