RU2628390C2 - Advanced coal gasification - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: gasifier for producing synthesis gas comprises an upper gasification zone in a fluidized bed, which has inlets to allow the introduction of materials selected from the group consisting of carbon, fine carbon particles of greater than 75 micrometers and less than 10 mm in size, gas and steam in fluid communication through a venturi nozzle with the lower gasification zone in co-current which has inlets to allow the introduction of materials selected from the group consisting of coal, fine coal particles of less than 75 micrometers in size, gas and steam.

EFFECT: increased efficiency of gasification, lower costs.

16 cl, 1 dwg

Description

BACKGROUND OF THE INVENTION

[0001] Coal gasification technologies are generally classified into three types: fixed bed gasifiers, such as those provided by Lurgi, fluidized-bed gasifiers, such as those provided by UGAS, and parallel flow gasifiers, as provided by Shell and General Electric . Fixed bed gasifiers have disadvantages in terms of low throughput of a single device and expensive synthesis gas and water processing systems. Fluidized bed gasifiers have problems unloading dry bottom ash carried away by high volatile ash and low carbon conversion. For gasifiers with a parallel flow, the main defects are a narrow range of suitable types of coal raw materials, and the size of the coal particles supplied to the gasifier should be less than 75 micrometers. In addition, large quantities of steam, for example, in TPRI gasifiers or other types of slurry gasifiers, or cold synthesis gas, such as Shell gasifiers, must be introduced for cooling to ensure that the temperature of the raw synthesis gas at the outlet of the gasifier is below 950 up to 1000 ° C due to downstream boiler requirements. This can significantly reduce the thermal efficiency of the gasification process.

[0002] The invention seeks to overcome these limitations by combining coal gasification technology with a normal fluidized bed and parallel flow gasification technology to improve their operation, efficiency and reduce costs.

SUMMARY OF THE INVENTION

[0003] In one embodiment of the invention, a gasifier is disclosed for producing a synthesis gas comprising an upper gasification zone in a fluidized bed in fluid communication through a venturi nozzle with a lower gasification zone in parallel flow.

[0004] The gasifier has walls with refractory lining in the upper gasification zone in the fluidized bed and water membrane walls in the lower gasification zone in parallel flow. The two gasification zones have tubes and openings to allow the introduction of materials for the formation of synthesis gas, namely coal, fine particles of coal and other reagents such as oxygen and steam. In particular, the upper gasification zone in the fluidized bed has inlets to allow the introduction of materials selected from the group consisting of coal, fine particles of coal, gas and steam, the gasification zone in parallel flow has inlets to allow the introduction of materials selected from the group, consisting of coal, small particles of coal, gas and steam.

[0005] Two gasification zones are connected using a venturi nozzle, which has a diameter narrower than both gasification zones. The gasification zone in a parallel flow has an opening in the lower part to allow liquid slag to be removed, while the gasification zone in the fluidized bed has an opening in the upper part to allow the production of produced synthesis gas, as well as fractions of fine particles and other produced gas .

[0006] In another embodiment of the invention, a method for producing synthesis gas is disclosed, comprising the steps of:

a) feeding small particles of coal, oxygen and steam simultaneously into the gasification zone in the fluidized bed and into the gasification zone in a parallel flow;

b) carrying out the reaction of small particles of coal in the presence of oxygen with steam to produce synthesis gas;

c) supplying synthesis gas from a gasification zone in a parallel flow to a gasification zone in a fluidized bed; and

d) the evolution of synthesis gas from the gasification zone in the fluidized bed.

[0007] The fine particles of coal that are supplied to the gasification zone in the fluidized bed are larger than those supplied to another zone, and they are larger than 75 micrometers in size. Small particles of coal fed into the gasification zone in a parallel flow are smaller than 75 micrometers in size.

[0008] the Gasification zone in the fluidized bed is at a temperature of about 1000 ° C or below the deformation temperature of coal ash, while the gasification zone in a parallel flow is at a temperature of about 1500 ° C or above the temperature of the liquid-melting state of coal ash.

[0009] The synthesis gas that is produced in both gasification zones is fed through a hole in the upper part of the gasification zone in the fluidized bed at a temperature of from about 900 to 1000 ° C. To the first stage of the cyclone, which will allow the synthesis gas, as well as the unreacted fine particles of coal that can be returned to the fluidized gasification zone.

[0010] Steam is introduced into said gasification zone in a parallel flow in order to advance the produced synthesis gas into said gasification zone in a fluidized bed.

[0011] The second cyclone will capture smaller unreacted coal particles, and they will be returned back to the gasification zone in a parallel flow.

[0012] The gasifier and methods of the invention can be used in various applications, such as integrated gas combined cycle, the conversion of coal into chemicals, the production of synthetic natural gas, etc.

Brief Description of the Drawings

[0013] The figure is a schematic representation of a two-stage coal gasifier according to the invention.

Detailed Description of Drawings

[0014] As shown in the figure, presents a two-stage coal gasifier. The gasification zone in the fluidized bed A is located above the gasification zone in the parallel flow B, being connected to the venturi C. The gasification zone in the fluidized bed has walls that contain refractory material D. The gasification zone in parallel flow has walls that contain an aqueous membrane wall E .

[0015] Gasification occurs in both zones so that coal particles of various particle size distributions come into contact with oxygen and / or steam. The products obtained include synthesis gas and a measured amount of carbon dioxide plus methane.

[0016] Coal having a particle size of less than 75 micrometers and small particles of coal recycled from a two-stage cyclone are introduced via line 9 into the gasification zone in a parallel stream B. Typically, the coal is transported in nitrogen or carbon dioxide. The gasification temperature is controlled at a level of about 1500 to 1600 ° C. above the temperature of the liquid-melting state of coal ash. The operating pressure is from about 3.0 to 4.0 MPa.

[0017] The steam that is introduced into the gasification zone in the parallel flow B is used to control the temperature of the gas and the flow rate entering the upper gasification zone in the fluidized bed A. The water membrane wall E is essentially a high pressure tube containing water , which helps to cool the gasification zone in parallel flow B. Steam is also generated inside the tubes. The tubes are provided with spikes that act as anchors for a thin layer of cast refractory material, which is typically silicon carbide. During operation of the gasifier, the cast refractory material would ideally be coated with a layer of solid slag over which liquid slag would pass to the bottom of gasification zone 10 in parallel flow B.

[0018] The hot synthesis gas that is generated enters the gasification zone in the fluidized bed A through a Venturi nozzle C, and the local temperature above the Venturi nozzle C is maintained at about the softening temperature of the coal ash. The Venturi nozzle C also functions as a “sorter” in the sense that particles of higher density collected together could fall into a section below the Venturi nozzle C and cause side reactions, thus becoming molten slag. The molten slag will exit the gasification zone in a parallel stream B through the hole 10 for quick cooling.

[0019] Coal having a larger particle size, above 75 micrometers and below 10 millimeters, is fed into the dense phase of the fluidized bed section in the gasification zone in fluidized bed A through line 1. The gas circulating the fluidized bed is oxygen and steam. The fine coal particles collected after the first cyclone stage (not shown) are recycled and re-introduced into the gasification zone in the fluidized bed A through line 2. Fluidizing oxygen and steam are introduced through lines 3, 4, 5 and 6. The crude produced synthesis gas, which is primarily hydrogen and carbon monoxide with some presence of methane, including, will leave the gasification zone in the fluidized bed A through hole 11 to the first stage of the cyclone. This synthesis gas reaction temperature is at a temperature of about 900 to 1000 ° C. or lower than the deformation temperature of coal ash. The flow of reacted residues or coal is controlled by a Venturi C. nozzle.

[0020] The gasification zone in the fluidized bed is usually created with a normal refractory wall, which consists of an outer layer of insulating bricks to protect the outer steel shell of the reactor from high temperatures, and an inner layer of denser bricks that can better withstand high temperatures and erosive conditions inside gasifier.

[0021] The cyclones that are used in the methods of the present invention are connected to the upper section of the gasifier, the gasification zone in the fluidized bed, through line 11 and to the bottom of the gasifier, the gasification zone in parallel flow B, through line 9. The first cyclone captures from 98 up to 99% of small particles of coal moving in the upper part of the gasifier through line 11. These small particles contain significant amounts of carbon and are recycled to the gasification zone in the fluidized bed A through line 2 for secondary reactions in gasification Ore. The second cyclone captures the remainder of the fine particles of coal, having a smaller particle size, which will reduce the reactivity during gasification. These smaller particles are recycled to the lower part of the gasification zone in parallel flow B through line 9, where they are reacted under more severe conditions to completely burn off the excess carbon present in the smaller coal particles.

[0022] Advantages of the present invention include liquid slag removal and a quick cooling procedure to eliminate the problem of discharging dry ash of a fluidized bed gasifier. Slag can simply be removed through the bottom 10 of the gasification zone in parallel flow B. Using a wider range of particles from the coal particle size distribution (PSD), both less than 75 micrometers and more than 75 micrometers, this will reduce the consumption of coal grinders , and also allow a wider range of coal raw materials, which can be used in the production of synthesis gas. The carbon conversion of fluidized bed gasifiers can be improved by increasing the ash temperature. Additionally, the thermal efficiency of the gasifier in parallel flow can be improved by eliminating the recycle of cold synthesis gas or additional steam. In addition, the amount of fly ash carried away from the fluidized bed gasifiers is reduced, and with this would be less disposal costs.

[0023] Although the present invention has been described with reference to specific embodiments thereof, it is apparent that numerous other forms and modifications of the invention will be apparent to those skilled in the art. The appended claims in this invention as a whole should be construed to cover all such obvious forms and modifications that fall within the spirit and scope of the present invention.

Claims (20)

1. A gasifier for producing synthesis gas, comprising an upper fluidized bed gasification zone that has inlets to provide introduction of materials selected from the group consisting of coal, fine particles of coal greater than 75 micrometers and less than 10 mm in size, gas and steam, in fluid communication through a venturi nozzle with a lower gasification zone in parallel flow, which has inlets to allow the introduction of materials selected from the group consisting of coal, small particles of coal less than 75 micrometers in size gas and steam. 2. The gasifier according to claim 1, wherein said upper gasification zone in the fluidized bed has walls with a refractory lining. 3. The gasifier according to claim 1, wherein said gasification zone in a parallel flow has water membrane walls. 4. The gasifier according to claim 1, wherein said Venturi nozzle has a diameter smaller than said upper gasification zone in a fluidized bed and said gasification zone in parallel flow. 5. The gasifier according to claim 1, wherein said gasification zone in a parallel flow has an opening in its lower part. 6. A method for producing synthesis gas, comprising the steps of: a) supplying small particles of coal, oxygen and steam simultaneously to the gasification zone in the fluidized bed and to the gasification zone in parallel flow, while the gasification zone in the fluidized bed is connected to the gasification zone in parallel flow through a Venturi nozzle, while the fine coal particles supplied in the gasification zone in the fluidized bed, more than 75 micrometers and less than 10 mm in size, and small particles of coal supplied to the gasification zone in a parallel flow, less than 75 micrometers in size; b) carrying out the reaction of small particles of coal in the presence of oxygen with steam to produce synthesis gas; c) supplying synthesis gas from a gasification zone in a parallel flow to a gasification zone in a fluidized bed; and d) the evolution of synthesis gas from the gasification zone in the fluidized bed. 7. The method according to p. 6, in which the said gasification zone in the fluidized bed is at a temperature of 1000 ° C. 8. The method of claim 6, wherein said venturi nozzle is smaller in diameter than said fluidized bed gasification zone and said parallel flow gasification zone. 9. The method according to p. 6, in which said gasification zone in a parallel flow is at a temperature of 1500 ° C or higher than the temperature of the liquid-melting state of coal ash. 10. The method of claim 6, wherein the fine coal particles supplied to said gasification zone in a parallel flow are less than 75 micrometers in size. 11. The method according to p. 6, in which liquid slag is supplied for rapid cooling from said gasification zone in a parallel flow. 12. The method of claim 6, wherein said synthesis gas is supplied to a first cyclone stage. 13. The method according to p. 12, in which the said synthesis gas is at a temperature of from 900 to 1000 ° C. 14. The method according to claim 6, in which the fine particles of coal that are recycled from the first stage of the cyclone are fed into the said gasification zone in the fluidized bed. 15. The method according to claim 6, in which the fine particles of coal that are recycled from the second stage of the cyclone are fed into said gasification zone in a parallel flow. 16. The method of claim 6, wherein the vapor is introduced into said gasification zone in a parallel flow to advance the produced synthesis gas to said gasification zone in a fluidized bed.

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