Patent Grant
9434896
The present application claims the priority of German Patent Application No. 102013215120.9, filed Aug. 1, 2013, the contents of which are incorporated by reference herein.
The invention relates to a multistage crude gas washing system having a high degree of separation of particles, in particular fine dust, during the production of crude gas rich in CO and H2 in an entrained flow gasification plant by reaction of ash, but also slag-forming fuels, under pressures up to 10 MPa and temperatures up to 1900° C.
Pulverized fuels are understood to include finely-ground coals of different degrees of carbonization, dusts made of biomasses, products of the thermal pretreatment such as coke, dried products by way of “torrefaction”, and fractions having high calorific value from municipal and industrial residual materials and waste materials. The pulverized fuels can be supplied as a gas-solid suspension or as a liquid-solid suspension to the gasification. The gasification reactors can be provided with a cooling screen or with a refractory lining, as disclosed in the patents DE 4446803 and EP 0677567. According to various systems introduced into technology, the crude gas and the molten liquid slag can be discharged separately or jointly in this case from the reaction chamber of the gasification device, as described in DE 19718131. A comprehensive description of the overall technology is found in J. Carl, P. Fritz, NOELL-KONVERSATIONSVERFAHREN, EF-Verlag, 1996, pages 25-53. Entrained flow gasification causes, as a result of the fuel particles, which are ground as fine as dust, and shorter reaction times in the gasification chamber, an increased dust fraction in the crude gas. This flue dust consists, in dependence on the reactivity of the fuel, of carbon black, unreacted fuel particles, and fine particles of slag and ash. The size varies between coarse particles having a diameter greater than 0.5 mm and fine particles having a diameter up to 0.1 μm. The separability of the particles from the crude gas is dependent on this diameter, but also on the composition thereof. Fundamentally, a differentiation can be made between carbon black and ash, on the one hand, and slag particles, on the other hand, wherein carbon black particles are generally smaller and more difficult to separate from the crude gas. Slag particles have a higher density and therefore a better separability, but in contrast thereto have a higher hardness and therefore an erosive effect. This results in increased wear in the classifying separators and lines which conduct crude gas, which can cause safety-relevant leaks and service life restrictions.
The previous prior art is documented in the patent DE 10 2005 041 930 and also in “Die Veredelung von Kohle [The Refinement of Coals]”, DGMK, Hamburg, December 2008, chapter “GSP-Verfahren [GSP Method]” pages 537-553, particularly in FIGS. 4.4.2.4.13 and 4.4.2.9.1. Accordingly, the gasification crude gas leaves the gasification chamber jointly with the slag formed from the fuel ash at temperatures of 1300-1900° C. and is cooled in a downstream quenching chamber by injection of excess water and freed of the slag and, to a small extent, of entrained dust. The further dust removal is performed in two Venturi washers connected in series, wherein the second washer has an adjustable throat to be able to keep the velocity in the throat constant even in the event of changing crude gas quantity and therefore to ensure a uniform velocity for the entrained dust. The gas purification was conceived for dust quantities up to 2 g/m3 under normal conditions and is intended to achieve a dust quantity of 1-3 mg/m3 under normal conditions at the outlet, which is necessary for disturbance-free operation of the downstream plants, such as CO conversion, synthesis, or gas turbines. To remove fine dusts, particularly of salt spray, a partial condenser is operated, in which the crude gas is cooled by 1-15° C., wherein the condensed water precipitates on the salt particles in particular and is removed from the crude gas stream by separation of the water droplets. For dust quantities greater than 2 g/m3 under normal conditions, this arrangement consisting of two Venturi washers and a partial condensation step is only partially adequate or is inadequate and can result in substantially higher dust concentrations in the intake of the CO conversion and also increased erosion in the Venturi washers and furthermore in soiling and blocking in the partial condenser and the downstream systems.
Proceeding from this prior art, it is the object of the invention to provide a gas purification system for an entrained flow gasification plant, which has a high separation rate of particles, in particular of fine dust, which, with a reliable operating mode, takes into consideration the different ash contents and ash properties of the fuels, and which has a high availability.
This object is achieved by a crude gas washing system having the features of the first invention.
To design the gasification plant for higher dust concentrations, consisting of coarse and fine particles, a selective separation of the particles is used. A combination of coarse-fine separators is proposed, which, in a first purification step, separates the coarse and particularly erosive particles in a robust and possibly multistage washing stage. This firstly has a quenching chamber, into which excess water is injected in finely dispersed form and in which, in addition to the cooling of the crude gas, a separation of very coarse dust particles occurs simultaneously. This is assisted by the arrangement of a hood over the crude gas discharge, which, in conjunction with a partition wall protruding downwards into the hood, forces the gas stream into a triple direction change and is additionally sprayed to avoid incrustations. Subsequently, the crude gas flows through a washing column having an immersion pipe, where it rises upward as a bubble column in the accumulated washing liquid. Due to the low velocity in the gas chamber located above it, dust-loaded water droplets are not entrained and fall back into the bubble column. All particles >10 μm are completely separated via this purification step. Smaller particles are separated in a following purification step, which consists of one or two successive Venturi washers. To also separate ultrafine particles <1 μm, the crude gas experiences direct cooling, but also indirect cooling of 1-15° C. by high-pressure injection of water 18, 20 or in a heat exchanger 19, respectively. The water loaded with fine dust and also condensate is subsequently separated from the crude gas in a fine droplet separator and returns into the water circuits. Ultrafine droplets having a large surface area, which can also absorb very fine particles, arise due to the high-pressure injection and the cooling. The fine droplet separator 21 can be equipped with washing surfaces 22 and is fitted in the top part with a coated demister packing 23. To counteract the hazard due to soiling of the droplet separator, it is coated using PTFE or a Teflon compound. Over 99.9% of the particles can be separated by the described combination of the mentioned cleaning stages.
The invention will be explained hereafter to an extent required for understanding on the basis of three figures and three exemplary embodiments. In the figures:
In the figures, identical reference signs identify identical elements.
80 Mg/h pulverized dust made of a lean coal are supplied to an entrained flow reactor having a gross output of 500 MW, as shown in
Since this dust results in disturbances in subsequent processes by way of erosion or deposits, a removal down to residual contents <1 mg/m3 under normal conditions is necessary, wherein the fine dust separation represents a special technological demand. To fulfill the stated goal, a multistage gas washing system is installed. The first stage comprises a modified quenching system and a downstream washing column, which operates as a bubble column. In the quenching chamber 6, crude gas and slag are firstly cooled to 220° C. and saturated with water vapor at the same time by injection of excess water. The separation of coarse dust already begins here due to a special modification of the quenching chamber 6. For this purpose, a hood having nozzles 9 is installed over the crude gas discharge 11, wherein a partition plate protrudes from below into the space enclosed by the hood. The crude gas leaving the quencher is forced into a triple direction change, whereby a further separation of particles occurs in conjunction with the nozzles 9. The hood can be drawn over a part or the entire circumference of the quenching chamber. Additional washing water can be introduced after the crude gas discharge 11 via an injection nozzle 10. Furthermore, the crude gas enters a washing column 12, is immersed in the water bath 13, and is guided upward as a bubble column into a free space at low crude gas velocity. In this first gas washing stage, approximately 30 mass-% of the coarse dust in the grain size range from 2500 to 10 μm is removed from the crude gas.
The second washing stage comprises a Venturi washing system, in which a first Venturi washer 14 having a fixed throat and a second Venturi washer 15 having a variable throat and water supply 16 are arranged.
The variable throat in the second Venturi washer 15 enables it to react to varying crude gas quantities. In this second washing stage, approximately 35 mass-% of the dust entrained in the crude gas in a grain size range up to 0.6 μm is separated.
In the third washing stage, the demanding fine dust separation is managed, which places special demands on the technology. For this purpose, solid-free washing water is injected in ultrafine dispersed form before and after a partial condenser 19 by high-pressure injection nozzles 18 and 20, to wet the entrained dust particles. The partial condenser 19 has the same task, in which, by way of cooling of the crude gas saturated with water vapor by 1 to 15° C., approximately 3 to 10 m3/h water vapor are formed with formation of similarly ultrafine droplets, wherein the fine dust particles represent condensation seeds for the water vapor and therefore the fine dust is incorporated in the condensed water. To separate the dust-carrying droplets, the third washing stage is terminated by a separation column 21, which is fitted with a plate column 22 and a plastic-coated demister 23. The crude gas, which is substantially freed of dust, leaves the separation chamber 21 via the gas discharge 24 and subsequently reaches further processes up to the generation of the final product. The carbon black water 25 separated from all of the washing stages and also the condensate and washing water 26 are returned after a separation of the entrained solids in the circuit back into the washing stages.
In an entrained flow gasification plant according to
In an entrained flow gasification plant according to
The invention is also provided by a method for dust separation from crude gases of entrained flow gasification of pneumatically or hydraulically supplied pulverized fuels under pressures up to 10 MPa and temperatures between 150 and 250° C. in the state of water-vapor saturation by a three-stage gas washing system, in which
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2013 215 120 | Aug 2013 | DE | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5453115 | Vuletic | Sep 1995 | A |
| 20070044381 | Holle et al. | Mar 2007 | A1 |
| 20110146485 | Kang | Jun 2011 | A1 |
| 20130303636 | Schmitt | Nov 2013 | A1 |
| 20140224636 | Shah | Aug 2014 | A1 |
| 20150041720 | Zhang | Feb 2015 | A1 |
| Number | Date | Country |
|---|---|---|
| 4446803 | May 1998 | DE |
| 19718131 | Oct 1999 | DE |
| 102005041930 | Mar 2007 | DE |
| 0677567 | Sep 1997 | EP |
| Entry |
|---|
| Carl J. et al: Noell-Konversionsverfahren zur Verwertung und Entsorgung von Abfällen, EF-Verlag für Energie-und Umwelttechnik GmbH, pp. 25-53, 1994. |
| Number | Date | Country | |
|---|---|---|---|
| 20150033627 A1 | Feb 2015 | US |
