JP2668266B2 - A method for changing contaminants in a high temperature and high pressure crude synthesis gas stream. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention introduces a finely divided solid fuel, such as pulverized coal, along with an oxygen-containing gas, through a burner to a reactor or gasifier from which a stream of hot crude syngas is contaminated in small quantities. It relates to a method for the partial combustion of said solid fuel which is discharged together with a substance, some of which may be in the form of particles having a sticky outer surface which is liable to adhere to equipment located downstream of the reactor.

Partial combustion involves reacting all fuel particles with hydrogen in a pure form or with sub-stoichiometric amounts of oxygen introduced in a mixture with other gases such as a nitrogen transport stream to oxidize the fuel with hydrogen. Partial oxidation to carbon. This partial fuel differs from full combustion, which completely oxidizes the fuel to carbon dioxide and water.

During the process of partial combustion of powdered coal in a gasifier, the coal minerals split into two streams as the coal is gasified. The produced molten slag falls to the bottom of the gasifier and is discharged there. Light particles of fly ash or mill slag, which also form, are carried out by a syngas stream piped through the top of the gasifier to a gas cooler, heat exchanger or waste heat boiler, where steam can be generated. .

During the evacuation of the product syngas from the gasifier, the problem arises that sticky fly ash particles settle on the walls of the outlet tube from the gasifier and are likely to solidify and clog the tube. Further, in some cases, sticky fly ash particles may deposit on the fins or tube bundles of the cooler, reducing the efficiency of the cooler. In each case, the process must be interrupted to periodically clean the equipment, which is unacceptable for the desired continuous operation of the process.

In an attempt to solve the above problems, it was previously proposed to form a gas shield on the inner wall of the outlet pipe from the gasifier to protect the inner wall from sticky particles adhering thereto. The product gas stream going to the cooler through the outlet tube will be surrounded by a cooler gas sheath over the entire length of the tube.
Thus, the sticky particles in the gas stream near the tube wall can be cooled to such an extent that when they encounter the surrounding cold gas sheath, the ashes particles solidify and lose their stickiness before they hit the wall. . According to that proposal, the cooler gas sheath had to be introduced via an annular slit at the upstream end of the outlet tube from the gasifier. However, it has been found that in some cases, the cooling gas shield or sheath is prematurely disturbed or collapsed, making the cooling operation of the sticky fly ash particles unsatisfactory.

The present invention produces a product gas (primarily carbon monoxide and hydrogen) by partially burning a finely divided carbonaceous fuel containing at least 1% by weight of the ash in a reactor or gasifier.
The product gas, together with it, as it leaves the reactor, sticky particles of fly ash or mill slag,
Alternatively, it is directed to such a partial combustion method for transporting an ash-forming component which may consist of alkali metal chlorides, silicon and / or aluminum oxides or other mineral species. At the temperatures prevailing in the reactor, the ashes are usually sticky. In particular, if the partial combustion is carried out by progressive gasification in a burner flame, the residence time in the gasifier or reactor is very short compared to gasification in a fluidized or moving bed process.
And the temperature is very high.

The ash formed during the gasification process is at least partially in liquid form at the conditions prevailing in the reactor, usually at a temperature of from 1050 to 2200 ° C. Since the ashes particles are not completely liquid, they will generally consist of at least partially molten slag, or combustion products or residues with a partially molten consistency. The high temperature of the reactor is sufficient to vaporize some other by-products that may take on a sticky form when cooled in the process equipment.

It is an object of the present invention to solidify at least the outer surface of normally sticky particles contained in the synthesis gas effluent exiting the reactor at temperatures above 1200 ° C.

Thus, the present invention provides substantially dry granular coal and oxygen to the gasification zone of the reactor at a coal to oxygen ratio that maintains a reducing atmosphere, and the crude synthesis gas, which is combined therewith. To produce a small amount of at least one contaminant impurity having a sticky outer surface that is likely to adhere to equipment downstream of the reactor when in solid particulate form), thereby producing a syngas that partially oxidizes coal at elevated temperatures. In the process of manufacture: a lower temperature quench gas stream is injected into the higher temperature synthesis gas stream substantially immediately after leaving the reactor to cool the sticky contaminant particles from the reactor. Reducing the stickiness of sticky particles of contaminants carried by the effluent of synthesis gas; and-a substantially straight conduit for the combined mixture of syngas and injected quench gas containing polluted sticky particles. Turbulence through Under conditions, to flow sufficient time to reduce at least the outer surface of the tacky thoroughly mixed to particles combined stream into a form that does not interfere with downstream equipment, to provide the manufacturing method characterized by.

In accordance with the present invention, it is desirable to have a long straight quench section of the tube forming the first section of the discharge tube from the reactor. The temperature of the product gas at this point is, for example,
1400 ° C. A stream of product gas, cooled several hundred degrees, is recycled from selected points in the process and injected as quench gas into the upstream end of the quench section of the reactor exhaust. By mixing the cold quench gas with the hot reactor effluent stream as it enters the quench section and flowing the mixture under turbulent flow conditions through a straight quench section of sufficient length, the hot synthesis product gas and The sticky particles carried thereby are thoroughly mixed with the cooler quench gas, thereby making the melted or sticky particles "freeze" or at least non-sticky enough that the outer surface of the particles does not stick to the walls of downstream equipment or piping. Enable you to become.

Accordingly, the present invention comprises: a) at least one gasifier or reactor for coal gasification producing syngas at a temperature of from 1505 ° C. to about 2200 ° C., said gasifier comprising a dry granular A coal gasification plant adapted to utilize coal and having a heat exchange surface adapted for indirect heat exchange with steam and water; b) mounted on and in flow communication with the gas outlet of a gasifier, lower temperature A long straight cooling or quench section or conduit which may be injected with the quench gas to mix with the hot effluent synthesis gas and the particles carried thereby under turbulent conditions; c) at least one in gas flow communication with the gasifier. A heat exchange section comprising at least one segment adapted to further cool the gas and the particles carried thereby; d) the heat exchange A gas purification section in flow communication with the reactor and including means for removing substantially all particles and various impurity gases such as H ₂ S and other contaminants from the synthesis gas; and e) re-cooling section. Designed for use in a syngas generation complex that includes a source of quench gas with reduced temperature and reduced particle content for circulation.

In particular, the present invention provides a) partial oxidation of coal at elevated temperatures by supplying dry granular coal and oxygen to the gasification zone, wherein the gasification zone preferably includes at least one burner for coal oxidation, The ratio is such that a reducing atmosphere is maintained, and a crude synthesis gas having a temperature of about 1050 ° C to about 2200 ° C is produced, and from the synthesis gas in the gasification zone is about 100 ° C to about 350 ° C. Removing the heat by indirect heat exchange with steam and water at a temperature of 0 ° C .; b) removing the crude synthesis gas and the sticky particles carried thereby by a long straight formed at the upstream end of the discharge pipe from the gasification zone (C) injecting a cooling quench gas into the quench chamber and mixing the cooling quench gas with hot synthesis gas under turbulent flow conditions to change at least the outer surface of the sticky particles to a non-sticky state; d) the crude synthesis gas from step c) Heat is removed from the syngas and the particulate matter carried thereby through a heat exchange zone of any suitable form known in the art; and e) particles are removed from the crude syngas, substantially particles. The present invention provides a method for producing syngas, comprising the steps of producing a syngas free of gas, a portion of which is adapted to be recycled and injected into a quench chamber.

In an advantageous embodiment of the invention, the crude syngas also contains a small amount of vaporized mineral matter and the reduction step is carried out by the injection of a certain volume of quench gas at a temperature lower than the syngas stream into which the quench gas is injected. And condensing.

In another advantageous embodiment of the present invention, a quench gas stream is injected into the crude syngas stream at a plurality of points around its periphery to provide a hot stream of syngas and the sticky particles carried thereby in the gas injection zone. Form a sheath of cooler quench gas around.

In yet another advantageous aspect of the present invention, the quench gas is a syngas with a small amount of solid particles of lower temperature contaminant impurities taken from a downstream point, said particles leaving the reactor and leaving the crude syngas stream. It has the same composition as at least one of the impurities therein.

The steam generated in the gasifier shell can be passed to a heat exchange zone where it can be superheated and sent for further use. Gasification may be carried out using any technique suitable for syngas production having a gasifier outlet temperature of about 1050 ° C to about 1650 ° C.

Although some fluid bed oxidizers are capable of producing such gas temperatures under the conditions described herein, the process is preferably carried out in a gasifier containing at least one burner. Such a process is advantageously a dry granular coal, i.e. about
It will involve the combustion of coal with oxygen content below 10% with oxygen. In some cases steam can be ignited to aid combustion. The type of coal used is not critical, but it is an advantage of the present invention that lower coals such as lignite or lignite can be used. The coal should be dried before use because the moisture content of the coal is too high to meet the above requirements. The atmosphere has a weight ratio of oxygen to moisture and ash-free coal of about 0.6 to 1.2, especially 0.9 to 1.0.
Adjustment to the range will maintain reducibility. The specific details of the equipment and procedures used do not form a part of this invention, but may be found in U.S. Pat.
0 and 4,458,607 may be used. However, in view of the high temperatures required, suitable structural materials such as Inconel and Incoloy 800, a high chromium-molybdenum steel, should be used to overheat for long exchanger life. By carrying out the advantageous procedures described herein, or by utilizing the advantageous structural aspects mentioned, as described above, of sticky substances which may adhere and / or occlude the feed tube or device. It is an advantage of the present invention that a particle-free synthesis gas stream is obtained.

The particular type of device used is not critical, within the stated limits. The key to the present invention, as already mentioned, is the wise integration of individual types of coal gasification technology or practices with clean delivery and equipment and operations or structures to achieve improved energy efficiency. The pressure used is not critical and those skilled in the art can provide appropriate pressure levels in the various devices of the present invention given the specified temperature.

The invention will be described in more detail, by way of example, with reference to the accompanying drawings, in which:

The figure is a schematic representation of the process flow type and illustrates the efficient integration of a specialized gasifier and a device for substantially removing particles of sticky material generated in the gasifier. . All the values specified below in the description thereof have been calculated or are merely descriptive.

Referring to FIG. 1, dry granular coal (average flow size of about 30
To 50 microns and a moisture content of less than about 10% by weight) via line (1) to the burner (2) of the gasifier (3). Only one burner (2) is shown for clarity. The gasifier (3) can be a vertical rectangular container, for example cylindrical in the burner area and having a generally conical or convex top and bottom, and a surrounding membrane wall structure (4) for cooling fluid circulation. ). Advantageously, the generally cylindrical reactor wall comprises a plurality of heat exchange tubes which are separated from each other by "membranes" or curved plates, which at their ends are of continuous flow of a heat exchange fluid such as water. And also has multiple inlets / outlets for the fluid in a manner well known in the art. Optionally, supply oxygen (5)
And the weight ratio of oxygen to coal not containing moisture and ash is, for example, about 0.9. The combustion produces a flame temperature of about 2200 ° C, and the gas temperature at the gasifier outlet is about 1250 ° C to about 1450 ° C. Adjustment of the gasifier and outlet temperatures is aided by the refrigerant in the membrane wall structure (4). The slag is discharged at the outlet (1a).

The hot crude syngas with impurities exits the gasifier (3) through a straight long quench line (8) of selected length, the interior of the quench line being carried by the crude syngas and thereby A quench chamber is formed where the impurities are quenched from the appropriate point in the process by the cooler syngas through line (6). The quench gas can be between 140 ° C and about 540 ° C. The quench line (8) may be jacketed for heat recovery (not shown). The quenched gas is then sent to a cooler or heat exchanger (7). The heat exchanger (7) is advantageously a multi-section exchanger, wherein the quenched syngas is cooled by the fluid in the tubes.

About 315 ° C to 140 in the low temperature section of heat exchanger (7)
The crude synthesis gas cooled to a temperature of ° C. is sent via a line (14) to a cleaning section (15) or a solids separator, where particles and various impurity gases such as H ₂ S can be removed. The details of the gas purification do not form a main part of the present invention.
The steam required for the cleaning action can come from what is produced by the whole process. The purified syngas exits from section (15) to line (17) and is ready for use. Dry solid impurities are discharged at the outlet (17a).

In FIG. 2, the same reference numbers as used in FIG. 1 apply. Instead of the quench line (8) of FIG. 1 running horizontally from the gasifier (3), the quench line (8) from the gasifier (3) of FIG. 2 is calculated vertically from the top of the gasifier. Is illustrated as extending a given distance. Rapid cooling line (8)
The length of the gas depends on the flow rate or flow rate in the quench line and the recirculated quench gas supply line, the temperature of the crude syngas and the quench gas from the gasifier, the nature of the vaporized impurities in the crude syngas to be condensed, It depends on many factors, such as the nature of the sticky Ash particles in the synthesis gas to be processed.

The test was performed in a pilot operation in which 200 tons / day of pulverized coal was burned with an equal weight of oxygen. The gasifier in one test ran at about 25 bar (range 10 to 100 bar) and the product gas exited the gasifier with contaminants at about 1450 ° C. After cleaning and cooling, a portion of the product gas stream at about 315 ° C is recycled as a quench gas at the upstream end of the quench section, which recirculates to form the substantially first section of the gas discharge line from the gasifier. did.

Equal masses of product gas and quench gas may be used. This ratio may vary and be used between 0.5 and 4.0 masses of quench gas for each mass of product gas depending on operating conditions, but to achieve sufficient cooling and turbulence in the quench chamber, The length should be 5 to 20 times the inside diameter of the line. This minimum length of the quench line advantageously has no bends in the particles until they pass through a point in the line where the particles are no longer sticky. At the high operating temperatures of the gasifier, certain impurities, such as silica and the lower oxides of many alkali metals, evaporate. These materials are then condensed and cooled in the quench section of the process equipment.
A quench section with a straight path 14 times the section diameter processed a 9 meter / second stream of thermal syngas in a system burning 200 tons / day of coal.

The other devices shown in FIG. 2 are the same as the components shown in FIG. FIG. 2 was included to show that the quench line (8) could exit vertically from the gasifier and enter the heat exchanger (7) from the top if desired.

[Brief description of the drawings]

FIG. 1 is a schematic flow diagram of a part of a process apparatus used for carrying out the method of the present invention, and FIG. 2 is a schematic diagram showing another arrangement of a device used for carrying out the method of the present invention. 2 ... burner, 3 ... gasifier, 7 ... heat exchanger, 8 ...
... quick cooling line.

Claims (7)

(57) [Claims] 1. A substantially dry granular coal and oxygen are fed to a gasification zone of a reactor in a ratio of coal and oxygen so as to maintain a reducing atmosphere to produce a crude syngas (this gas is Along with that, it also carries a small amount of at least one contaminating impurity having a sticky outer surface which, when in solid particle form, tends to adhere to equipment downstream of the reactor), a stream of cooler quench gas at a higher temperature Cooling the sticky contaminant particles into the syngas stream substantially immediately after leaving the reactor to cool the sticky particles of the contaminants carried by the effluent stream of syngas from the reactor. In a method for producing a synthesis gas, which comprises partially oxidizing coal at a high temperature, which comprises lowering,
A combined mixture of syngas containing contaminated sticky particles and an injected quench gas is mixed through a substantially straight conduit under turbulent flow conditions to thoroughly mix the combined flow to reduce the stickiness of at least the outer surface of the particles. The method of claim 1 wherein the flow is for a time sufficient to reduce the device to a non-disturbing form. 2. The crude syngas also contains a small amount of vaporized mineral matter, and the reduction step comprises vaporizing the mineral matter by injecting a volume of quench gas at a temperature lower than the syngas stream into which the quench gas is injected. The method of claim 1 including condensing. 3. The method according to claim 1, wherein the quench gas is a low-temperature product gas free of water and particles produced by the method. 4. A quench gas stream is injected into the crude syngas stream at a plurality of points around its perimeter to cool the quench stream around the hot stream of syngas and the sticky particles carried thereby in the gas injection zone. 4. The method according to claim 1, wherein a gas sheath is formed. 5. A process according to any one of claims 1 to 4, characterized in that the mass of quench gas injected into the crude syngas stream is 0.5 to 4 times the mass of syngas. 6. A process according to claim 1, wherein the length of the straight section of the conduit downstream of the quench gas injection point is 5 to 20 times the diameter of the conduit. . 7. The quench gas is a synthesis gas comprising a small amount of solid particles of lower temperature contaminant impurities taken from a downstream point, said particles comprising at least one of the impurities in the effluent crude synthesis gas stream exiting the reactor. A method according to any of claims 1 to 6, characterized in that it has the same composition as one.