CA2537787A1

CA2537787A1 - Method and device for producing synthesis gases by partial oxidation of slurries made from fuels containing ash with partial quenching and waste heat recovery

Info

Publication number: CA2537787A1
Application number: CA002537787A
Authority: CA
Inventors: Manfred Schingnitz; Friedemann Mehlhose; Torsten Bergt
Original assignee: Siemens Fuel Gasification Technology GmbH and Co KG
Current assignee: Siemens AG
Priority date: 2005-09-07
Filing date: 2006-02-27
Publication date: 2007-03-07
Also published as: US20070051043A1; DE202005021662U1; CN1928028A; DE102005042640A1; AU2006201144A1; ZA200607265B

Abstract

This invention relates to a method and a device for the gasification of solid fuels such as bituminous coal and coke such as bituminous coal, lignite, and biomass, as well as petroleum coke, that are finely ground and mixed with water or oil to make fuel liquid suspensions, so-called slurries, and their gasification together with an oxidizing medium containing free oxygen by partial oxidation at pressures between atmospheric pressure and 100 bar, and at temperatures between 1200 and 1900 °C, in a flue stream reactor, consisting of the process steps of slurry preparation and infeed to the reactor, gasification in a flue stream reactor with cooled reaction chamber contour, partial quenching, waste heat recovery, and wet or dry dust separation, with the crude gas being pretreated so that it can be fed to other technological steps such as crude gas conversion or desulfurization.

Description

METHOD AND DEVICE FOR PRODUCING SYNTHESIS GASES BY
PARTIAL OXIDATION OF SLURRIES MADE FROM FUELS CONTAINING
ASH WITH PARTIAL QUENCHING AND WASTE HEAT RECOVERY
This invention relates to pulverized fuel gasification methods and to devices for implementing those methods.
The autothermic flue stream gasification of solid, liquid, and gaseous fuels has been known in the field of gas production for years. The ratio of fuel to gasification medium containing oxygen is chosen so that higher carbon compounds are completely cracked for reasons of synthesis gas quality into synthesis gas components such as CO
and H2, and the inorganic components are discharged as molten slag; see J.
Carl, P. Fritz, NOELL-KONVERSIONSVERFAHREN, EF-Verlag fiir Energie- and Umwelttechnik GmbH, 1996, p. 33 and p. 73.
According to various systems used in the industry, gasification gas and molten slags can be discharged together from the reaction chamber of the gasification device, as shown in DE 197 131 A1. Either systems with refractory linings or cooled systems are used for the inner confinement of the reaction chamber structure of the gasification system; see DE 4446 803 A1.
EP 0677 567 B1 and WO 96/17904 show a method in which the gasification chamber is confined by a refractory lining. This has the drawback that the refractory masonry is loosened by the liquid slag formed during gasification, which leads to rapid wear and high repair costs. This wear process increases with increasing ash content.
Thus, such gasification systems have a limited service life before replacing the lining.
Also, the gasification temperature and the ash content of the fuel are limited. Feeding in the fuel as a coal-water slurry causes considerable losses of efficiency - see C. Higman and M. van der Burgt, "Gasification", Verlag ELSEVIER, USA, 2003 - which can be prevented or reduced by using oil as a carrier medium or by preheating the coal-water slurry. A quenching or cooling system is also described, by which the hot gasification gas and the liquid slag are carried off together through a conduit that begins at the bottom of the reaction chamber, and are fed into a water bath. This joint discharge of gasification gas and slag can lead to plugging of the conduit and thus to limited availability.

DE 3534015 Al shows a method in which the gasification media, powdered coal and oxidizing medium containing oxygen, are introduced into the reaction chamber through multiple burners in such a way that the flames are mutually deflected.
The gasification gas loaded with powdered dust flows upward and the slag flows downward into a slag-cooling system. As a rule, there is a device above the gasification chamber for indirect cooling and utilization of the waste heat. However, because of entrained liquid slag particles there is the danger of deposition and coating of heat exchanger surfaces, which hinders heat transfer and may lead to plugging of the pipe system and/or erosion. The danger of plugging is counteracted by cooling the hot crude gas with a circulated cooling gas.
Ch. Higman and M. van der Burgt in "Gasification", page 124, Verlag Elsevier 2003, describe a method in which the hot gasification gas leaves the gasifier together with the liquid slag and directly enters a waste heat boiler positioned perpendicularly below it, in which the crude gas and the slag are cooled with utilization of the waste heat to produce steam. The slag is collected in a water bath, while the cooled crude gas leaves the waste heat boiler from the side. A series of drawbacks detract from the advantage of waste heat recovery by this system. To be mentioned here in particular is the formation of deposits on the heat exchanger tubes, which lead to hindrance of heat transfer and to corrosion and erosion, and thus to lack of availability.
CN 200 4200 200 7.1 describes a "Solid Pulverized Fuel Gasifier", in which the powdered coal is fed in pneumatically and gasification gas and liquefied slag are introduced into a water bath through a central pipe for further cooling. This central discharge in the central pipe mentioned is susceptible to plugging which interferes with the overall operation, and reduces the availability of the entire system.
It is the object of this invention, proceeding from this state of the art, to provide a gasification method and device which take into account the different ash contents of fuels and has high availability, with reliable operation.
This object is achieved with a gasification method in accordance with the invention including the principle process steps of fuel slurry preparation, fuel infeed to the reactor, gasification reaction by partial oxidation of powdered fuels containing ash with a gasification medium containing free oxygen, at high temperatures and elevated pressure, partial quenching, crude gas scrubbing, and partial condensation, wherein the crude gas scrubbing and partial condensation can be replaced by a mechanical dust separation, to produce gases containing CO and H2.
To achieve long operating times, the pressurized jacket of the gasification reactor has to be protected reliably against the action of the crude gas and against the high gasification temperatures of 1200 - 1900 °C. This is done by confining the reaction or gasification chamber with a cooled tubular shield that is hung in the pressurized jacket.
The annular gap between tubular shield and pressurized jacket is flushed.
The fuel slurry is brought to the gasification pressure by pump transport and is fed to the head of the reactor through burners. One or more fuels or varieties of coal can be gasified at the same time. The crude gas leaves the gasification chamber together with the liquefied slag at the bottom of the reactor and is then partially cooled to 700 °C to 1100 °C by injecting water, and is freed of entrained fines after recovering the waste heat. The scrubbed crude gas is then fed to further treatment steps.
The preferred gasification method for the gasification of solid fuels containing 1 S ash with an oxidizing medium containing oxygen, in a gasification chamber designed as a flue stream reactor, at pressures between atmospheric pressure and 100 bar, in which the reaction chamber contour is confined by a cooling system, with the pressure in the cooling system always being chosen to be higher than the pressure in the reaction chamber, is distinguished by the following features:
The fuel, e.g. bituminous coal, bituminous coke and lignite coke, as well as biomass coke and/or petroleum coke and/or their mixtures, is pulverized to a grain size of < 500 pm, preferably < 200 pm, and mixed to make a fuel-in-water or fuel-in-oil suspension, a so-called slurry, by adding liquids such as water or oil. Stable solids concentrations of up to 70 wt.% are achieved when using water as the Garner medium with added surfactants. These are brought to the desired gasification pressure of up to a maximum of 100 bar by means of suitable pumps, and are fed for the gasification reaction through suitable burners that are attached at the head of the gasification reactor.
The fuel concentration in the slurry and the amount of flowing slurry are monitored, measured, and regulated by measurement devices, control devices, and monitors.
An oxidizing medium containing free oxygen is fed to the burner at the same time, and the fuel is converted into crude synthesis gas by partial oxidation. The gasification takes place at temperatures between 1,200 °C and 1,900 °C at pressures up to 100 har. The reactor is equipped with a cooling shield that consists of water-cooled pipes welded gas-tight.
The hot crude synthesis gas leaves the gasification chamber together with the liquid slag formed from the fuel ash, and arrives at a chamber perpendicularly under it, in which partial quenching occurs by injecting water or by feeding in a cold gas, whereby it is cooled to temperatures between 700 °C and 1,100 °C. At this temperature, the entrained liquid slag has been cooled to the extent that it can no longer adhere to metallic surfaces. The crude gas cooled to temperatures of 700 °C and 1,100 °C then arrives at a waste heat boiler together with the likewise cooled solid slag, to utilize the l0 sensible heat for steam production. This preceding partial quenching or partial cooling prevents or sharply reduces the risk of slag caking on the waste heat collecting pipes.
The water or recycled gas condensate needed for the partial quenching is fed in through nozzles that are located directly on the jacket. The cooled slag is collected in a water bath located at the bottom of the waste heat boiler. The crude gas, cooled to 200 °C -300 °C, leaves the waste heat boiler at the side and reaches a crude gas scrubber, suitably a Venturi scrubber. The entrained dust is thereby removed down to a grain size of about 20 p.m. This degree of purity is still inadequate for carrying out subsequent catalytic processes, for example crude gas conversion. It also has to be considered that salt mists are also entrained in the crude gas, which have detached from the powdered fuel during gasification and are carried off with the crude gas. To remove both the fines < 20 ~m and the salt mists, the scrubbed crude gas is fed to a condensation step in which the crude gas is chilled indirectly to about 5 °C to 10 °C.
Water is thereby condensed from the crude gas saturated with water vapor, which absorbs the described fine dust and salt particles. The condensed water containing the dust and salt particles is separated in a following separator. The crude gas purified in this way can then be fed directly, for example, to a crude gas converter or desulfurization system.
Instead of the scrubbing and condensation steps, a mechanical dust separator can be provided that operates at 200 °C to 300 °C, for which centrifugal separators or filter systems can be used.
The invention is described in further detail below with reference to Figures and an exemplary embodiment. The Figures show:
Figure 1: Block diagram of the technology;

Figure 2: Gasification reactor with partial quenching and perpendicularly arranged waste heat boiler;
Figure 3: Gasification reactor with partial quenching and adjacent waste heat boiler.
Example 320 tons/hour of bituminous coal with a composition of C 71.5 wt.%
H 4.2 wt.%
O 9.1 wt.
N 0.7 wt.%
S 1.5 wt.%
Cl 0.03 wt.%, an ash content of 11.5 wt.%, and a moisture content of 7.8 wt.%, is to be gasified at a pressure of 40 bar. T'he caloric value of the coal is 25,600 kJ/kg. The gasification takes place at 1,450 °C. 245,000 m3 (standard)/h of oxygen is needed for the gasification. The coal is first fed to a state-of the-art grinder in which it is pulverized to a grain size range between 0 and 200 p,m, and is then mixed in a special system 1 according to Fig. 1 with water and added surfactants to make a stable coal dust in water suspension, the so-called slurry. The solids concentration in this slurry is 63 wt.%, and the amount of slurry is 485 tons/hour. The slurry is brought to the desired gasification pressure of 100 bar by means of a pump suitable for pumping solid-liquid suspensions, and is fed to the burner of the gasification reactor 2 of Fig. 1 through the supply line 1.1, with the amount being monitored, measured, and regulated. To conserve oxygen, the slurry can be preheated up to 400 °C, depending on the gasification pressure, prior to being fed into the gasification reactor 2.
Figs. 2 and 3 show the gasification reactor. The slurry flowing to the gasification reactor through the feed line 1.1 at 465 tonslhour is subjected to partial oxidation at 1450 °C along with the 245,000 m3 (standard)/hour of oxygen flowing to the gasification chamber 2.3 through the line 2.1, with 565,000 m3 (standard)lhour of crude gas being formed with the following composition:
HZ 18.5 vol.%
CO 70.5 vol.%
S

COZ 6.1 vol.%
NZ 2.3 vol.%
NH3 0.003 vol.%
HCN 0.002 vol.%
S H2S 0.5 vol.%
COS 0.07 vol.%.
The gasification chamber 2.3 is confined by a cooling shield 2.4 that consists of a water-cooled tube system welded gas-tight. The crude gas together with the liquid slag flows through the outlet opening 2.5 into the chamber 3.1 for partial quenching/partial cooling of the crude gas to temperatures of 700 °C - 1,100 °C.
At this temperature, along with the crude gas, the slag is also cooled to such an extent that it cannot be deposited in the pipes 4.1 of the waste heat boiler that follows according to Fig. 1. The steam generated in the waste heat boiler 4 is utilized in the process to preheat the oxidizing medium containing oxygen or as a gasification moderator to preheat the slurry.
The slag is collected in a water bath 4.2 located at the bottom of the waste heat boiler and is discharged through 4.3. The crude gas leaves the waste heat boiler through 4.4 and arrives at the crude gas scrubber 5 according to Fig. 1. The waste heat boiler 4, however, can be located according to Fig. 3 directly beneath the gasification reactor 2 and the partial quencher 3, but also, as shown in Fig. 4, beside it. In this case, there is a slag discharge 4.3 beneath the partial quencher 3 and also one below the waste heat boiler 4.6.
The crude gas leaving the waste heat boiler 4 through the outlet 4.4 then arrives at the crude gas scrubber S according to Fig. 1, which is an adjustable Venturi scrubber to which is fed about 100 m3lh of wash water. The wash water is freed of absorbed solids in the usual way and is fed again to the Venturi scrubber. The wash water can be preheated in order to wet the crude gas further at the same time as the washing. To remove fines < 20 pm in size and salt mists not separated in the Venturi scrubber, the water-washed crude gas is subjected to a partial condensation 6 according to Fig. 1, with the crude gas being chilled indirectly to about 5-10°C. The finest dust and salt particles are taken up by the water vapor condensing out during the chilling and thus removed from the crude gas. The crude gas cleansed of solids then has the following composition:
HZ 13.4 vol.%
CO 51.4 vol.%

' CA 02537787 2006-02-27 COZ 4.5 vol.%

NZ 1.5 vol.%

NH3 0.0022 vol.%

HCN 0.0012 vol.%

HZS 0.36 vol.%

COS 0.05 vol.%

H20 37.30 vol.%

The purified, wet crude as amounts to 775,000 m3 (standard)lhour.
g It can be directly sent to a crude gas converter or to other treatment steps.

List of reference symbols used 1 Slurry preparation and infeed 1.1 Slurry line 2 Reactor 2.1 Line for oxygen 2.2 Burner 2.3 Gasification chamber 2.4 Cooling shield 2.5 Outlet opening 3 Quenching cooler 3.1 Quenching chamber 3.2 Nozzles in 3 3.4 Transfer line from 3 to 4 4 Waste heat boiler 4.1 Cooling pipes in the waste heat boiler 4 4.2 Water bath with slag in 4 4.3 Slag discharge from 4 4.4 Opening from 4 to the crude gas scrubber 5 4.5 Water bath with slag 4 4.6 Slag discharge from 4 5 Crude gas scrubber 6 Partial condenser

Claims

1. Method for the gasification of fuels such as bituminous coals and cokes such as bituminous coal, lignite, biomass, and petroleum coke in the flue stream in a reactor, comprising the steps of - preparing a slurry of a pulverized fuel with a grain size < 200 µm, preferably < 100 µm, and water with added surfactant to obtain a fuel-in-water slurry with a solids concentration of 40-70 wt.%, - bringing the slurry to a gasification pressure of 100 bar by pumping, for which the slurry can be preheated to temperatures up to 400 °C, - feeding the slurry to the reactor through a supply pipe together with an oxidizing medium containing free oxygen for subjecting the fuel to partial oxidation in the reaction chamber at pressures between atmospheric pressure and 100 bar and at temperatures between 1,200 and 1,900 degrees, a reaction chamber contour being confined by a cooling shield;
- transferring molten ash of the fuel through a discharge device to a quenching chamber of a quenching cooler along with the generated hot gasification crude gas, - carrying out a partial quenching of the crude gas to temperatures between 700 and 1,100 °C, - cooling the partially quenched crude gas in a waste heat boiler to temperatures between 150 and 400 °C with generation of steam, - subjecting the cooled crude gas to a crude gas scrubbing and partial condensation, or to a dry mechanical dust separation by centrifugal force or filtration, to separate entrained dust, and - subjecting the cooled crude gas freed of dust to further treatment steps such as crude gas conversion or desulfurization.

2. Method according to Claim 1, wherein the crude gas scrubbing is a single-or multiple-stage Venturi scrubbing.

3. Method according to Claim 1 or 2, wherein fresh water, or recycled condensates that result from the cooling of the crude gas, are used in the crude gas scrubbing step.

4. Method according to any one of Claims 1 to 3, wherein the waste heat boiler is operated at temperatures of 700 to 1,100 °C.

5. Method according to any one of Claims 1 to 4, wherein the crude gas scrubbing takes place at temperatures of 150 to 300 °C.

6. Method according to any one of Claims 1 to 5, wherein multiple Venturi scrubbers are used which are supplied with circulated water or recycled condensate.

7. Method according to any one of Claims 1 to 6, wherein the fuel is supplied to the reactor as a fuel-in-water slurry.

8. Method according to any one of Claims 1 to 7, wherein the fuel slurry is supplied to the gasification reactor through one or more burners.

9. Method according to any one of Claims 1 to 8, comprising the further step of discharging the granulated slag through one or more outlets from the quenching chamber.

10. Method according to any one of Claims 1 to 9, wherein the partially quenched crude gas is discharged from the quenching chamber through one or more gas outlets.

11. Method according to any one of Claims 1 to 10, wherein one or more varieties of coal are gasified at the same time.

12. Method according to any one of Claims 1 to 11, wherein the amount of slurry transported in the supply pipe is measured, monitored, and regulated.

13. Device for implementing a method according to any one of Claims 1 to 12, comprising:
a feed system for producing and feeding a fuel slurry;
- a reactor for the gasification of fuel with an oxidizing medium containing free oxygen, a supply pipe for transporting the slurried fuel from the feed system to the reactor and a feed line for supplying the oxidizing medium to the reactor, at least one burner for supplying the fuel and the oxidizing medium into a reaction chamber of the reactor, the reaction chamber having a cooling shield consisting of water-cooled pipes welded gas-tight and an outlet for gasification gas, - a quenching cooler with no internals for partial quenching of the gasification gas, the quenching cooler having nozzles arranged in one or more nozzle rings for spraying the water necessary for partial quenching, the nozzles being integrally incorporated in an inner jacket of the quenching cooler, - a waste heat boiler downstream of the quenching cooler, - a crude gas scrubber, and a partial condenser, wherein the crude gas scrubber and partial condenser can be replaced or supplemented by a device for dry dust separation.

14. Device according to Claim 13, wherein a reaction chamber of the quenching cooler is connected directly to the waste heat boiler, in which sensible heat of the crude gas is utilized through heat recovery tubes to produce steam, and the cooler has discharge openings at a bottom of the cooler for withdrawal of the crude gas and slag into a water bath.

15. Device according to Claim 13 or 14, wherein the crude gas scrubber is followed by a partial condensation system for further purification of the crude gas.

16. Device according to Claim 15, wherein a single- or multiple-stage Venturi scrubber is used as the crude gas scrubber.

17. Device according to Claim 13 or 14, wherein a mechanical dry dust separator is used for gas purification.

18. Device according to any one of claims 13 to 17, further comprising additional gas treatment stages such as a crude gas converter or a desulfurization system connected in line after the scrubber and partial condenser or the mechanical dry dust separator.

19. Device for implementing a method according to any one of Claims 1 to 12, comprising a feed system for producing and feeding a fuel slurry, - a reactor for the gasification of the fuel with an oxidizing medium containing free oxygen, a supply pipe for transporting the slurried fuel from the feed system to the reactor and a feed line for supplying the oxidizing medium to the reactor, at least one burner for supplying the fuel and the oxidizing medium into the reaction chamber of the reactor, the reaction chamber having a cooling shield consisting of water-cooled pipes welded gas-tight and a discharge device for gasification gas, - a quenching cooler for receiving and partial cooling of the gasification gas, from which the partially cooled crude gas flows through a transfer line to a waste heat boiler, equipped with boiler tubes and utilizing the sensible heat of the crude gas to produce steam, - a crude gas scrubber, and - at least one of a partial condensation system and a mechanical filtration dust separator following the crude gas scrubber.

20. Device according to Claim 19, further comprising a water bath in each of the quencher and the waste heat boiler, for collecting the cooled slag.

21. Device according to Claim 19 or 20, further comprising a device for discharging slag provided on each of the quencher and the waste heat boiler.