NO155696B - PROCEDURE AND APPARATUS FOR COOLING AND CLEANING A HOT GAS FLOW. - Google Patents

Description

The present invention relates to a method and an apparatus for cooling and purifying a hot gas stream, produced by partial oxidation of an ash-containing, solid, carbonaceous fuel, where a hot raw gas stream is produced which essentially comprises H2, CO and CO2 as well as smaller amounts of entrained other gases as well as slag and/or particulate matter.

In the partial oxidation of liquid and solid hydrocarbon-containing fuels with steam and free oxygen to produce gaseous mixtures containing carbon monoxide and hydrogen, the gases leave the gas generator at a temperature in the range of 954 to 1648 °C. Depending on the supply and operating conditions, the gas stream leaving the gas generator carries different amounts of slag and solids, such as soot and ash. It is often desirable to reduce the concentration of these accompanying materials. By removing solids from the gas stream, one can e.g. increase the lifetime of the downstream equipment that comes into contact with the gas stream, e.g. the lifetime of gas coolers and turbines. Removal of solids from the synthesis gas will also prevent clogging of the catalyst bed. In addition, a gas can be produced that is environmentally acceptable.

In US-PS 2 871 114 it is stated that the gas and slag from the gasification of coal is led into a slag container, which is arranged directly below the generator. Water is supplied to the slag container for collection and solidification of the slag that falls out of the gas stream. The gas stream leaves the slag container and is directed to a cooling accumulator container where the gas is brought into intimate contact with water and cooled to a temperature in the range of 148 - 315'C. The gas stream leaving the cooling tank is saturated with rFjO. Furthermore, all free heat in the gas flow is then dispersed in the cooling water at a relatively low temperature level. When the raw gas stream leaving a coal-fired generator at a temperature above approx. 926 °C is introduced directly to a gas cooler, the slag that accompanies the gas stream will be deposited on the inner surfaces of the gas cooler and contaminate the heat exchanger surfaces. In US-PS 4 054 424, nothing is indicated about means for removing slag from the device.

In contrast to what has hitherto been the case, the impure or fresh synthesis gas according to the invention is purified without cooling in water and is therefore not saturated. It is also cooled to a temperature in the range 648-989° C and below the temperature at which the slag begins to deform. The thermal energy in the gas stream can be recovered at a high temperature level. The solidifying slag particles are removed from the device. In this way, contamination of equipment located downstream of the energy recovery from the hot gas stream is avoided.

The present invention relates to a method for cooling and purifying a hot gas stream, produced by partial oxidation of an ash-containing, solid, carbonaceous fuel, where

1) particles of the solid fuel are reacted with a gas, containing free oxygen, with or without a temperature moderator in a refractory lined gas generator with downward flow at a temperature in the range 925-1705"C and a pressure in the range 10-200 atm for producing a fresh gas stream containing H2, CO, CO2 and at least one material from the group comprising H2O, H2S, COS, CH4, NH3, N2 and A and containing molten slag and/or particulate material and this method is characterized in that the fresh gas flow is led through a heat-insulated transfer line and a first gas inlet to the lower chamber in a gas-solid separation zone comprising a closed, vertical, cylindrical, heat-insulated pressure vessel, containing said lower chamber which is coaxial with the pressure vessel's vertical central axis and communicates with a coaxial upper chamber, where the lower and upper chambers are connected by a coaxial throat ring passage and where part of the slag and/or p the article material falls out with the help of gravity and falls to the bottom of the lower chamber, the gas mixture is led from the lower chamber up through the throat ring to the upper chamber in countercurrent with the slag drop and then possibly to a gas-solid separation device which is placed in the upper chamber , slag and/or particulate matter are separated from the gas mixture in the upper chamber and removed from the container via an outlet in the bottom of the lower chamber, and purified gas is removed from the upper chamber and emptied through an outlet at the top of the vertical container. As mentioned in the introduction, the invention also relates to an apparatus for carrying out the above-mentioned method for cooling and purifying a hot gas stream, produced by partial oxidation of solid, carbonaceous fuel, and this apparatus is characterized by the fact that it comprises 1) a partial oxidation gas generator for the production of the hot gas stream, 2) a separate, closed, vertical, cylindrical pressure vessel, which is internally lined with refractory material with high resistance to high temperatures, with a coaxial lower gas-gas quench cooling and solids-separation chamber in communication with a coaxial upper chamber, a reduced diameter coaxial throttle passage connecting the lower and upper chambers, 3) a first gas inlet nozzle connected to the gas generator for introducing the hot fresh gas stream into the lower chamber, a second gas inlet nozzle directly opposite and coaxial with the first gas inlet nozzle for simultaneous introduction of a cooled and purified gas flow in the lower comb r, arranged so that the two gas streams bounce against each other, 4) upper outlet means in the upper part of the upper chamber for emptying a cooled and purified gas stream, and 5) a bottom outlet at the bottom of the lower chamber for emptying solids and slag.

Hot raw gas can be introduced into the lower chamber where the temperature of the gas is reduced to a temperature in the area of approx. 648 to 982 °C and below the temperature at which the slag begins to deform upon impact against and direct heat exchange with an oppositely directed, coaxial flow of cooled, purified and compressed recirculating cooling gas. Solid particles are separated from this raw gas stream and emptied through an outlet at the bottom of the lower chamber. A throat ring passage separates the lower chamber from the upper chamber. The stream of cooled gas leaving the turbulent lower chamber passes up through the throat in countercurrent to solid slag droplets which are separated above by gravity. If desired, a solids separator from the group of single-stage and multi-stage cyclones, impact separators, filters and combinations thereof can be provided in the upper chamber for the removal of residual carbonaceous fine particles and solid slag droplets, which may remain in the cooled gas stream . In a preferred embodiment, a solids separator from the group of single-stage cyclone, multi-stage cyclone and combinations thereof is mounted in the upper chamber. A cooled and purified gas stream is discharged from the upper chamber and subjected to further cooling and, if necessary, to further purification. A portion of this gas stream is then compressed and sent back to the lower chamber as the aforementioned cooled and purified recirculating cooling gas stream.

Some embodiments of the invention will now be described in more detail with reference to the drawing, where

Fig. 1 is a schematic representation of the gas-gas extinguishing-cooling and solids separator apparatus according to the invention in vertical section, Fig. 2 is a schematic representation of a plant where the apparatus according to fig. 1 is used for carrying out an embodiment of the method according to the invention, Fig. 3 is a schematic representation of another plant, where the apparatus according to fig. 1 is used for carrying out another embodiment according to the invention.

As mentioned, the invention relates to an improved continuous method and an apparatus for cooling and cleaning a hot fresh gas stream which mainly contains H2, CO, CO2 and H2O and which also contains accompanying solids and molten slag. The apparatus is particularly suitable for cooling and cleaning the hot, raw gas stream which is produced by partial oxidation of a solid carbonaceous fuel.

The recovery of energy from the hot fresh gas stream from the partial oxidation gas generator will increase the heat efficiency of the gasification process. Steam can thus be produced as a by-product for use in the process or for other applications by heat exchange between the hot gas stream and water in a gas cooler. However, energy recovery is made difficult by the fact that in the generator's exhaust gases there are drops of molten slag that originate from the coalescence of the ash content of the coal that is fed to the generator. The present invention provides an apparatus and a method for solidifying the molten slag droplets and removing the resulting particulate material from the gases so that energy recovery will thereby be facilitated. Common problems with slag build-up are avoided by the present invention by solidifying the slag particles before they hit solid surfaces. Furthermore, solid surfaces have been removed from the point where slag cooling begins.

Depending on the amount of unconverted solids and ash in the fresh gas stream leaving the gas generator, the apparatus and method according to the invention can be used on its own or follow a preliminary separation of solids and liquid slag from the gases. While the apparatus according to the invention can be used on its own or follow a preliminary separation of solids and liquid slag from the gases. While the apparatus according to the invention can be used for treating the hot, fresh gas outlet stream from virtually any type of gas generator, it is particularly suitable for use downstream of a gas generator for partial oxidation. An example of such a gas generator is shown and discussed in US-PS 2,829,957. In one embodiment, the new gas-gas extinguishing cooling and solids separation device can be connected in front of a gas cooler in a device that includes a gas generator for the production of synthesis gas and a gas cooler. A gas generator for partial oxidation and a waste heat boiler can e.g. be connected by a filled room with or without a separable collection pan, as shown in US-PS 3 565 588. In such a case, the device according to the invention can be connected to the line immediately upstream of the gas cooler or the waste heat boiler in which the supplied water is converted into steam. With the help of the invention, combustion residues are removed in the gas stream, the boiler's pipes are not contaminated and the lifetime of the convection type heat exchangers is extended.

The apparatus according to the invention comprises a closed, cylindrical, vertical pressure vessel, the inner walls of which are thermally insulated. The container can e.g. inside be lined with refractory material that resists high temperatures. In the container there are two cylindrical, vertical chambers, which are lined with refractory material and run coaxially with the central axis of the container and communicate with each other. These chambers are a lower cooling chamber and an upper solids separation chamber. A coaxial throat ring passage connects the two chambers. The longitudinal axis of at least one pair of opposing, coaxial, internally insulated inlet nozzles passes through the walls of the lower chamber. The inlet nozzles are 180° apart and are arranged on opposite sides of the lower chamber. The hot, fresh gas flow is led through an inlet nozzle and a relatively cooler and cleaner recycling flow of cooling gas is led through the opposite inlet nozzle. The two flows collide in the lower chamber and this frontal collision causes a turbulent gas mixture. The strong turbulence results in rapid mixing of the oppositely directed gas flows and in direct heat exchange.

Although the following description applies to a single nozzle pair, which is the usual embodiment, a plurality of inlet nozzle pairs, e.g. 2-10, of a similar type are used. The pairs of nozzles can be arranged at regular intervals around the container. The longitudinal axis of the inlet nozzles can be inclined to direct the fresh gas flow upwards, as shown in the drawing, or it can run horizontally. Alternatively, the longitudinal axis can be inclined to direct the gas flow downwards, if this suits the general shape of the gas generator and the cooling-separator apparatus better. Thus, the longitudinal axis that is common to each pair of inlet nozzles is in the same plane as the container's vertical center axis and can have any angle in the range approx. 30° to 150° with and measured clockwise from the vertical center axis of the container. This angle is appropriate in the area approx. 40° to 135°, e.g. 45°, as shown in the drawing. The actual angle is a function of factors such as the temperature and velocity of the gas flow and the composition and concentration as well as the properties of the accompanying substances to be removed. When the fresh gas flow e.g. contains slag that is very fluid, the longitudinal axis of the fresh gas inlet nozzle can point upwards at an angle of approx. 45°, measured clockwise from the vertical center axis of the container. Much of the slag will then flow down the transmission line and be collected in a slag pan upstream of the device according to the invention. When the liquid slag, on the other hand, is viscous, the slag can be helped to flow down by the fresh gas inlet nozzle pointing downwards, e.g. about. 135°, measured clockwise from the vertical center axis of the container. The high speed of the hot fresh gas stream through the inlet nozzle and gravity will then help to move the viscous liquid slag to the lower chamber, where it solidifies and is separated from the gas stream by gravity.

The hot fresh gas stream enters through the inlet nozzle at a temperature in the range 926-1704°C, e.g. at 1093-1648°C, particularly in the range 1260-1537°C, and preferably 1371°C. The pressure is in the range 10 to 200 atmospheres, e.g. 25-85 atmospheres and typically at approx. 40 atmospheres. The speed is in the range 3-30 m/second, e.g. 6-15 m/sec. and typically approx. 9 m/sec. The solids concentration in the incoming hot fresh gas stream can be in the range 3.5 mg/stand, dm^ to 141.2 mg/stand, dm^, e.g. 8.8 mg/stand, dm^ to 70.6 mg/stand. dm^. The particle size can be in the range of 40 to 1000 pm or roughly equivalent to Stairmand's coarse dust - "Filtration and Separation", vol 7, no 1, p 53, 1970 Uplands Press Ltd. Croydon, London.

The cooled, purified recirculation stream of refrigerant gas entering through the opposite inlet nozzle is obtained from at least one part, i.e. 20-80 mol%, e.g. 30-65 mol-% and typically approx. 60 mol% of upper outlet flow from the device according to the invention, with or without further cleaning and/or cooling. The temperature of the cooling gas is in the range of approx. 93-426'C, e.g. about. 148-315° C, typically approx. 176°C. The mass flow rate and/or speed of the hot fresh gas stream and the cooled, purified, recycled cooling gas is regulated so that the amount of velocity for the two oppositely directed, incoming gas streams is approximately the same.

In the following Table I, columns 3 and 4 show temperatures and compositions of typical gas mixtures that are produced when flows of fresh synthesis gas and cooled, purified, recycled cooling gas collide in the lower cooling chamber at the temperatures shown in column 1 and 2.

The ends of each pair of opposing inlet nozzles preferably do not project appreciably into the chamber. The opposing inlet nozzles preferably end in a plane perpendicular to their center line. In this way, deviations from the concentricity of these currents are reduced to a minimum. The gas jets leaving the opposite nozzles travel approx. 1.5-3 m, e.g. 2.4 m, before they bounce straight towards each other. The strong turbulence that occurs in the lower chamber promotes rapid mixing of the gas streams. This promotes heat transfer from gas to particle. By turbulent mixing of the cooled and cooling gas flow, solidification of the outer layer of slag particles thus takes place before the slag can bounce against solid surfaces. A gas mixture is formed with a temperature below the temperature at which the slag that comes together with the fresh gas stream begins to deform, i.e. 648-982" C, typically approx. 760°C. The supplied slag is cooled and a solidified shell forms on the slag particles and prevents them from sticking to the inner walls of the apparatus or to any fixed structural element in the apparatus. In an exemplary embodiment, from 1 to 50 volume % of the cooling gas that is recycled into the cooling separation device according to the invention via several tangential nozzles, which are placed at the top of the lower chamber and/or at the bottom of the upper chamber. In this way, the upwardly flowing gases are given a vortex movement. This will further creating a protective zone of colder gas along the inner wall of the throat ring and above.

Solid particles, i.e. unreacted coal, carbon particles, carbon containing particulate solids, slag particles, ash and pieces of refractory material are separated from the fresh gas flow and fall to the bottom of the lower chamber where they are removed through an outlet in the bottom of the pressure vessel. A sluice funnel device is connected to the bottom outlet so that the pressure is maintained in the container. Preferably, the bottom of the pressure vessel has a low point which is connected to the bottom outlet. The bottom of the pressure vessel can e.g. be designed as a truncated cone or it can be spherical or elliptical.

The throat ring forms a corridor connecting the upper and lower chambers. It is used to dampen the turbulence in the gas flow from the lower chamber. In this way, stable conditions are achieved on the upward flow of the gas. Compared to the turbulence in the lower chamber, the gas rising through the upper chamber is relatively calm. This promotes gravitational settling of solid particles which fall through the throat ring to the bottom of the lower chamber. The throat ring is preferably made of a refractory material. Its diameter is smaller than both the upper and lower chamber diameters. The diameters of the upper and lower chambers depend on factors such as the velocity of the gas stream flowing in the chambers and the size of the accompanying particles. The ratio between the upper chamber diameter (du) and the lower chamber diameter (di) is in the range 1.0 to 1.5, typically approx. 1.0. The ratio between the diameter of the throat ring (dc) and the diameter of the lower chamber (dj) is in the range 0.5-0.9, e.g. 0.6-0.8, preferably 0.75.

Although the upper chamber may be empty to provide additional room for gravitational deposition of accompanying solids, it is preferably fitted with at least 1, e.g. 2-12, preferably 2 gas-solid separation means in the upper chamber for removing at least part of the solid particles remaining in the gas stream. Typical gas-solid separation means that can be used in the upper chamber can be selected from the group: single-stage cyclone separators, multi-stage cyclone separators, bounce separators, filters and combinations thereof. In a preferred embodiment, single-stage or multi-stage cyclone separators or combinations thereof are used in the upper chamber as gas-solid separators. The actual number of gas-solid separators employed will depend on such factors as upper chamber dimensions and the actual volume velocity of the gas stream approaching the entrance to the gas-solid separators at the top of the upper chamber. At this point, the concentration of solids is in the range 1.76 mg/dm^ to 70.6 mg/dm^. The particle size is in the range of 40 to 200 micrometres or roughly equivalent to Stairmand's fine dust. Any conventional, continuous gas-solid separation device can be used which will remove over 65% by weight of the solid particles in the gas stream and which will withstand the operating conditions in the upper chamber. The pressure drop through the gas-solid separation means is preferably less than 20 inlet velocity heights. (See: "Chemical Engineer's Handbook", Perry and Chilton, 5th ed. 1973, McGrawHill, pp. 5-20 to 5-38). Furthermore, the separation means should withstand hot, erosive gas flows at a temperature of up to approx. 1093°C, possibly up to 1648°C.

Gas-solid separators that can be used in the upper chamber can be selected from the group: single-stage cyclone separators, bounce separators for gas-solids, filters and combinations of these.

Preferred gas-solid separators are of the cyclone type. A cyclone is, in principle, a deposition chamber where the thin-deck raft is replaced by centrifugal acceleration. In dry-type cyclone separators, the fresh gas stream, which is enriched in particulate solids, enters a cylindrical-conical chamber tangentially through one or more inlets at the upper end. The path of the gas comprises a double vortex where the fresh gas flows spirally up inside to a central or concentric gas outlet pipe at the top. The clean gas stream leaves the cyclones and therefore passes out of the container through an outlet at the top. As a result of their inertia, the solid particles will tend to move towards the separator wall in the cyclone, from which wall they are led to an outlet pipe via a central outlet at the bottom. Small particles will form accumulations that can be easily removed by the cyclone. The outlet pipe or drop pipe extends down into the pressure vessel from the bottom of the cyclone, preferably below the longitudinal axes of the inlet nozzles in the lower chamber, and below the highly turbulent area. Solids in particulate form that are separated from in the cyclone can thereby be led through the downpipe and emptied through a control valve to the bottom of the lower chamber, below the zone where violent mixing takes place. The downpipe can be removed from the path of the slag droplets in one or more of the following ways: the downpipe can be placed close to the walls of the container, as it spans the axes of the inlet nozzles for hot gas and cooling gas, or ceramic downpipes can be arranged in the refractory wall. Alternatively, the downpipes can be made shorter, so that they end somewhere above the upper part of the lower chamber.

It can e.g. at least one single-stage cyclone is mounted in the upper chamber with its inlet facing the horizontal, circular component of a rising spiral flow pattern, which will exist in the embodiment where part of the cooling gas enters the container tangentially, or it will otherwise be created by using the cyclone's inlet flow. In the case of a number of parallel-connected single-stage cyclones, the gas outlet pipe for each cyclone can empty into a common internal collection chamber which is supported in the upper chamber. The purified gas stream leaves the collection chamber through the gas outlet at the top of the upper chamber. In another embodiment, at least one multi-stage cyclone unit is arranged in the upper chamber. In this case, the partially purified gas stream that is discharged from a first-stage internal cyclone is directed to a second-stage cyclone which is supported in the upper chamber. The clean gas stream from each second-stage cyclone is emptied into a common collecting chamber which is supported at the top of the upper chamber. From there, the clean gas is discharged through an outlet at the top of the upper chamber. In other embodiments, one- or two-stage cyclones are arranged outside the upper chamber, with or without cyclones in the upper chamber. Cyclones and prell separators are discussed in more detail in the "Chemical Engineer's Handbook" Perry and Chilton, 5th ed. 1973, McGrav-Hill Book Co. pp. 20-80 to 20-87.

An outlet or drop pipe extends down into the pressure vessel from the bottom of the cyclone and preferably to a location below the axes of the inlet nozzles in the lower chamber and below the highly turbulent area. Solid substances in particulate form that are separated in the cyclone can then pass through the downpipe and empty through a control valve in the downpipe to the bottom of the lower chamber, below the zone of violent mixing. The downpipe can run outside the path of the slag droplets in one of the following ways: the downpipe can be located close to the walls of the container and span the axes of the inlet nozzles for hot gas and cooling gas, or there can be ceramic downpipes in the refractory wall. Alternatively, the downpipes can be truncated, so that it ends somewhere above the upper part of the lower chamber.

The upward surface velocity of the gas flow in the upper chamber and the diameter and height of the upper chamber are preferably such that the inlet to the cyclone separator (or separators) lies above the throat ring by a distance that at least corresponds to the transport release height (TDH), also called equilibrium release height. Above TBH, the degree of reduction of entrainment of solid particles in the gas stream is close to zero. Particle entrainment varies with factors such as the viscosity, density and speed of the gas flow, with the specific weight and size distribution of the solid particles and with the height above the throttle. The velocity of the gas flow through the throat ring can vary in the range of 0.6 to 1.5 m per second. The velocity of the gas flow through the upper chamber's net base diameter can vary in the range of 0.3 to 0.9 m/sec. Transport The release height can vary in the range 3.0-7.6 m. If the speed of the gas flow e.g. is 1.06 m/sec. through the throat ring and approx. 0.6 m/sec. total base cross-section in upper chamber or 0.76 m/sec. net base cross-section of upper chamber, the transport release height can be 4-6 m in an upper chamber that has an internal diameter of 3-4.5 m.

The gas stream leaving the plenum chamber at the top of the cyclone separators passes through an outlet in the upper part of the upper chamber at a temperature in the range 648-982°C. The pressure drop in the synthesis gas flow that passes through the gas-solid separator device according to the invention is less than approx. 0.35 kg/cm^. The concentration of solids in the outlet stream from the separation vessel is in the range 1.1-24.7 mg/dm^. Part of this gas stream is subjected to further cooling and, with or without further purification, is directed downstream by conventional means to form the previously mentioned recycled cooling gas. It can e.g. a conventional gas-solid separation device is connected in the line downstream of the gas-gas quenching and solid-solid separation apparatus. This gas-solid separation device can be selected from the group of single or multi-stage cyclones, bounce separators, filters, electrostatic separators and combinations thereof.

With the aid of the apparatus according to the invention, from 85 to 95% by weight of accompanying solids and slag can be advantageously removed from the hot fresh gas stream leaving the partial oxidation gas generator, while at the same time the temperature of the gas stream is reduced to a temperature that downstream of the apparatus for recovery of energy from the hot gas stream can withstand. Preferably no liquid washing liquid is used. In this way, the free heat in the hot gas stream is not lost by evaporation of washing liquid, which can then contaminate the gas stream. The free heat remaining in the purified gas stream, which leaves the apparatus according to the invention and is or is not further cooled, purified or both downstream, can later be recovered in a downstream convection-type waste heat boiler. Thus, H2O or boiler feed water can be converted into steam by indirect heat exchange. The steam can be used elsewhere in the process, e.g. for heating, power generation or in the gas generator. Alternatively or in addition, energy recovery can be carried out in another way. Part of the cooled and purified gas flow is led, e.g. through an expansion turbine for the production of mechanical energy, electrical energy or both.

It should be noted that the amount of slag that accompanies the hot fresh gas stream that enters the lower chamber of the above-mentioned apparatus for cleaning a fresh gas stream can be reduced to a minimum in certain embodiments according to the invention or eliminated by controlling the composition of the solid carbonaceous fuel and the temperature in the carburettor. In such cases, gas-gas bouncing and quenching of the incoming hot fresh gas stream with a cooled and purified recycled gas stream can advantageously be reduced to a minimum or completely omitted. In such a case, the gas flow will leave the gas purification apparatus at essentially the same temperature as the incoming hot, fresh gas flow, minus normal heat loss. All other aspects of the pre-chamber are the same as for the gas-gas quench type.

With methods according to the invention, the heat efficiency of the partial oxidation-gasification can be increased by recovering energy from the hot, fresh gas stream by producing steam as a by-product for use in the process or for removal by heat exchange of the hot gas stream, in some embodiments with water in a gas cooler and in other embodiments with boiler feed water and steam in a main gas cooling zone. As mentioned above, energy recovery is made more difficult by the presence of small droplets of molten slag and/or solid particles in the exhaust gases from the generator. In the present invention, the slag droplets are partially solidified and removed before they meet heat exchange surfaces. By partially solidifying the slag particles before they bounce against solid surfaces and/or by removing solid particles in the gas flow, common problems with contamination of gas coolers are avoided. Solid surfaces have been removed from the point where slag gap cooling takes place. Relatively simple, inexpensive gas coolers are used for the heat exchange. The invention facilitates the recovery of heat energy from the hot gases.

Although these special energy recovery gas cooling devices could be used to treat the hot, fresh exhaust gas stream from virtually any type of gas generator, they are particularly suited for use downstream of a partial oxidation gas generator. An example of such a gas generator is shown and discussed in US-PS 2 871 114. Here, a burner is placed in the upper part of the gas generator for supplying the gas streams. A typical ring burner is shown in US-PS 2,928,460.

The hot fresh gas flow that leaves the diversion chamber through the refractory-lined passage enters directly into the inlet of the above-mentioned apparatus for cooling and cleaning the fresh gas flow (hereinafter referred to as "the pre-chamber"), where further accompanying slag and/or solid particles are removed and where the gas flow is possibly partially cooled. Contamination of the boiler tubes in the main gas cooling zone is thereby reduced and the maintenance problem is thus reduced to a minimum. The antechamber is located in front of the main gas cooling zone.

Instead of or in addition to the gas-solid separation means which are placed in the upper chamber of the antechamber, in some embodiments there may be external gas-solid separation means downstream of the antechamber and upstream of the main gas cooling zone. The gas-solid separation devices which are arranged outside the pre-chamber can be selected from the group of single or multi-stage cyclone separators, gas-solid bounce separators, filters, electrostatic precipitation devices and combinations thereof.

In preferred embodiments of the invention, a main gas cooling zone is arranged directly downstream of the pre-chamber or any solids separation devices which are arranged downstream of the pre-chamber. The temperature of the gas stream entering the main gas cooling zone is in the range 648-1648"C, e.g. 648-982"C, preferably approx. 871 °C. The concentration of solids in this gas stream is in the range 0.35 mg/dnv<*> to 24.7 mg/dnA Then most of the free heat in the gas stream is removed in the main gas cooling zone which comprises one or more interconnected jacket tubes -gas coolers, i.e. heat exchangers. Each gas cooler has one or more passages on the shell and tube sides and preferably has fixed tube plates. Compared to the gas coolers used in the method according to the invention, the conventional synthesis gas coolers for the production of high-pressure steam are of the spiral tube or serpentine tube type. Gas coolers with such tube spirals are difficult to clean and maintain. They are relatively expensive and they become clogged easily, if the solid charge of the gas is noticeable. When boilers with such spirals need servicing, this leads to costly downtime. These problems are advantageously avoided by the method according to the invention, which comprises the use of one or more gas coolers each comprising a jacket and a plurality of parallel straight tubes.

The gas coolers are preferably arranged for two-stage cooling - a first or high-temperature stage and a second or low-temperature stage. In the first or high-temperature stage, a preferred design example comprises a shell-tube heat exchanger with fixed tube plates and with a passage on the shell and tube sides. The fresh gas is located on the pipe side and the refrigerant on the jacket side. The inlet and outlet ends of the straight, parallel tubes in the tube bundle located in the pressure jacket are supported at each end by a tube plate. The pipe ends are connected to respective inlets and outlets, i.e. stationary heads at the front and rear end. The inlet and outlet zones and the inlet pipe plate are lined with refractory material. Metal or ceramic bushings can also be used in the inlet pipe plate to provide additional heat protection for the pipes. The first heat exchanger is made as short as possible so that it will be easier to clean the pipes and so that the thermal expansion stress to which the fixed pipe plates are exposed is reduced to a minimum. The tube plates themselves are designed so that they bend slightly to eliminate excessive heat stress. The outer diameter of the tube is in the range of 1.5 to 2.0 times the tube diameter in the second stage cooler. This is done so that the possibility of clogging of the heat exchanger is reduced to a minimum. The gas velocity is high enough to keep the pollution problems within acceptable limits. Further details of the shell-tube construction of heat exchangers with fixed tubes and plates appear from pages 11-5 to 11-6, fig. 11-2 (b) and pages 11-10 to 11-18 of "Chemical Engineers' Handbook", Perry and Chilton, 5th ed. McGraw-Hill Book Co. New York.

In some embodiments, the second or low-temperature stage of the gas cooler may comprise two tube-side passages and one mantle-side passage. This heat exchanger is designed similar to the gas cooler for the first stage. But in this heat exchanger, smaller pipes can be used as a result of fewer clogging problems at lower temperatures. In this way, the surface area available for a given casing diameter can be increased. The diameters in the first stage gas cooler can e.g. be 7.6 cm (outer diameter) while the outer diameter of second stage gas coolers can be 5.1 cm.

The direction of the longitudinal axes of the straight tube heat exchangers can be horizontal, vertical or a combination of both directions. However, as shown in the drawing, the longitudinal axes of the shell-and-tube heat exchangers are preferably vertical. This enables gravitational separation of accompanying solid particles from the gas stream and easy removal of particulate material from an outlet at the lower end of the gas cooler. Furthermore, the inlet to the first stage gas cooler is preferably arranged directly above the pre-chamber or any additional solids removal device that follows the pre-chamber.

The preferred combination of shell-and-tube heat exchangers with vertical tubes with one or two tube side passages and fixed tube plates is shown in the drawing and will be discussed in more detail below. In the aforementioned embodiment, the hot gas stream is cooled in the first stage gas cooler to a temperature in the range 426 to 648 °C, e.g. 482 to 593 °C, again approximately 537 °C. This happens by indirect heat exchange with a refrigerant, i.e. boiler feed water or steam. The hot gas stream passes through a bundle of parallel, straight tubes. The single passage of straight pipes will distribute the heat stress equally over the fixed pipe plates. In the second-stage cooler, the temperature of the gas stream is reduced to 8 to 49°C, e.g. about. 11 °C from the selected steam temperature. The temperature of the gas stream leaving the second-stage cooler is e.g. in the range 232 to 310" C, e.g. approx. 287° C. By using two passages on the tube side in the second stage gas cooler, the tube length is effectively increased for a given jacket size. This results in savings in construction. More passages on the tube side are used to reduce the thermal stress on the fixed tube sheets as a result of expansion.More tube passages will also reduce ground plan sar eals or heights, depending on the orientation of the heat exchanger.

In other embodiments, the second, or low-temperature stage, for the gas cooler may comprise one or more shell-and-tube heat exchangers with straight tubes and fixed tube plates and with one or more passages on the shell and tube sides. Although the design of the second stage gas cooler(s) is in many respects similar to the design of the first stage gas cooler, smaller pipes can be used in this as there is less risk of clogging at lower temperatures. In this way, the surface area available for a given casing diameter can be increased. For example, the tube diameters in the first stage gas cooler may be 7.6 cm in outer diameter, while the outer diameter of the tubes in the second stage gas cooler may be 5.1 cm. In a preferred design example, there are two gas coolers in the second stage. One of the gas coolers superheats saturated steam, which is produced in the other gas coolers. In another embodiment, the superheater is arranged in the first stage.

The direction of the straight longitudinal axes of the shell-and-tube heat exchangers in the main gas cooling zone can be horizontal, vertical or a mixture of the two directions. As shown in the drawing, the longitudinal axes for all shell-and-tube heat exchangers with straight tubes are vertical. An upright position allows separation of entrained solid particles from the gas stream by gravity and easy removal of particulate material from an outlet at the lower end of the gas cooler. The inlet to the first stage gas cooler is furthermore preferably arranged directly above the pre-chamber or any additional solids removal device that follows the pre-chamber.

For the production of superheated steam in the main gas cooling zone, the preferred combination of gas coolers comprises three interconnected shell-and-tube heat exchangers with straight, vertical tubes but one or two tube-side passages, one shell-side passage and with fixed tube plates, which shown in the drawing. The construction of these gas coolers will be discussed in more detail below. During operation of the preferred embodiment, the hot gas stream is passed at a temperature of 648-1648°C, e.g. 648-982°C, preferably approx. 871 ° C, and a pressure in the range of 10 to 200 atmospheres in indirect heat exchange with the boiler feed water up through the parallel, straight tubes on the tube side of the first vertical gas cooler which has a passage on the tube side and one on the jacket side. The partially cooled gas stream leaves the first gas cooler at a temperature in the range 593-1093°C, e.g. 593-871 °C, preferably at approx. 648°C. The coolant i.e. boiler feedwater from a steam drum is introduced into the first gas cooler on the mantle side at a temperature in the range 10-315" C, e.g. at 254-315° C, preferably at around 298°C and exits as saturated steam at a temperature in the range 221-315° C, eg 254-315° C, preferably 298° C. The saturated steam is stored in the storage drum.

At least a part, i.e. 50-100% by volume, e.g. 80-100% by volume and preferably 90% by volume of the gas flow leaving the first gas cooler is introduced into the second vertical gas cooler as hot flow. Preferably, the entire hot gas flow from the first cooler is introduced into the straight pipe of the second cooler. The part of the gas that is led past the second cooler is determined by the desired temperature in the steam leaving the second gas cooler. The hot gas stream is led down through the parallel, straight tubes for one pass on the tube side and jacket side of the second gas cooler in indirect heat exchange with saturated steam, and leaves the gas cooler at a temperature in the range 454-954"CC, e.g. 454-732 'C, preferably about 510° C. At least a part, i.e. 80 to 100% by volume, about 90% by volume, of the saturated steam produced by the process and stored in the steam drum is introduced into other gas coolers on the jacket side which refrigerant. Superheated steam is removed from other gas coolers with 37-226 °C, e.g. 37-210 °C, preferably approx. 137 °C superheat. This by-product in the form of superheated steam can be used elsewhere in the process as a heating medium or working fluid in a turbine for the production of mechanical and/or electrical energy Excess superheated steam can be led elsewhere.

The partially cooled gas flow leaving the second gas cooler is mixed with the rest of the partially cooled gas flow from the first gas cooler which is connected past the second gas cooler. This gas stream is conducted at a temperature in the range 426-648°C, e.g. at approx. 537'C through the parallel, straight tubes for the two passages on the tube side and one passage on the jacket side for a vertical, third gas cooler in indirect heat exchange with boiler feedwater. The gas flow passes up through the pipes in the first pipe side sweep and then down through the pipes in the second pipe side sweep. The partially cooled gas stream leaves the third gas cooler at a temperature in the range of 232-371 °C, e.g. 265-371 °C, preferably at about 310 °C. The pressure drop through the main gas cooling zone is 0.07-0, 70 kg/cm^. The coolant, i.e. the boiler feed water from the steam drum, is introduced into the third gas cooler on the jacket side at a temperature in the range 10-315 °C and leaves the gas cooler as saturated steam at a temperature in the range 221-315 °C, e.g. 254 -315° C, preferably 298° C. The saturated steam is stored in the steam drum.

By using two sweeps on the pipe side in the third gas cooler, the pipe length is effectively increased for a given jacket size. Construction savings are thereby achieved. Several sweeps on the pipe side are used to reduce the thermal stresses on the fixed pipe plates as a result of expansion. More tube sweeps will also reduce the ground plan area or heights, depending on the orientation of the heat exchanger.

Typically, superheated steam is produced by heating saturated steam in a conventional externally fired heating device. In a variation of the method according to the invention, superheated steam leaving the second gas cooler, as previously mentioned, is led through an externally fired heating device, where it receives additional heat. By means of this combination of steam heaters, i.e. with superheat from 148-298 °C, e.g. from 148-265 "C, preferably 221 °C. In this way, the fired heating device effect is also reduced to a minimum.

As a temperature control of the superheated steam, water can, if desired, be injected into the superheated steam leaving the fired heating device to lower the degree of superheating, while the fuel speed of the fired heating device is adjusted.

The second and third gas coolers in the low temperature stage are designed to withstand the maximum inlet gas temperature. If the pipes for the first gas cooler in the high-temperature stage, e.g. becomes contaminated, so that the temperature of the gas stream emerging from the first gas cooler rises, an optionally usable emergency injection circuit is provided to protect the second and third gas coolers from damage. When the inlet temperature of the gas exceeds a safe maximum temperature, a temperature sensor in the gas inlet line in one or both gas coolers will give a signal to a temperature control device, so that it opens a valve in the auxiliary high-pressure gas line. The control valve is opened and steam is injected into the hot gas stream, thereby lowering the temperature of the gas stream.

In the method according to the invention, "flue pipe" means that the hot gas always passes through the set of parallel, straight gas cooler pipes. The coolant passes on the jacket side. The internal flow of the refrigerant in the gas cooler is controlled by elements such as: one or more inlet and outlet nozzles and their location; and the number, location and design of transverse baffles, bulkheads and dams. In addition to guiding the coolant on the jacket side through a fixed path, the diverting plates usually have the function of supporting the straight pipes in the pipe set.

Pipes with a small diameter (2.5-10 cm outer diameter) can be used in the construction of the gas coolers according to the invention. The pipe diameter is chosen on the basis of an economic analysis of its effect on heat transfer, pressure drop, contamination and clogging tendencies. Long pipes provide potential savings for the construction at higher pressures, as the investment per unit area for heat transfer is lower for longer heat exchangers. The gas and refrigerant velocities in the heat exchanger are limited so that destructive mechanical damage due to vibration or erosion is avoided, to maintain a permissible pressure drop and to control the build-up of deposits. The velocity of the hot gas through the straight tubes with an outer diameter of 5.1 cm, depending on the temperature and pressure at any given point in the heat exchanger. Pipes with a larger diameter are used when heavy contamination is expected and to facilitate the mechanical cleaning of the pipes on the inside. Tube-to-tube plate connection can be achieved by a combination of tube end welding and roll expansion. The pipes can be arranged on a triangular, square or twisted square module ("pitch"). The center distance of the pipes, the type of guide plate and the distances between guide plates are chosen so that good coolant circulation is achieved and that places with particularly strong heat generation are formed on the inlet pipe plate. The heat exchanger's shell size is directly dependent on the number of tubes and the tube module. Usually, the mantle for the heat exchanger used in connection with the method according to the invention is made of high-quality carbon steel. When high-pressure steam is formed or superheated, steel alloys can be used to reduce the required jacket thickness and to reduce the costs for the plant.

The inlet and outlet parts of the gas coolers will normally consist of steel alloy due to the temperature and the partial hydrogen pressure in the fresh gas. The pipe materials will usually be steel alloys for similar reasons. But the last passages for the second stage gas cooler can in some cases consist of carbon steel. The flow patterns between fluid on the casing and tube side include counter flow, co flow, simultaneous flow and combinations. Relevant factors that affect the size of the heat exchangers and thus the costs include: pressure drop, gas composition, gas and coolant flow rates, calculated mean values for temperature difference and pollution factors. An optimal heat exchanger construction is the function of many of the previously discussed, interacting parameters.

Although many suitable liquid or gaseous refrigerants can be passed on the jacket side of the gas cooler, boiler feedwater or steam are preferred refrigerants. In this way, saturated or superheated steam can be produced as a by-product at temperatures in the range 271-482 °C and pressure close to 100 atmospheres, for use elsewhere in the plant or outside.

The following advantages are obtained by passing the hot gas stream containing solids through the present gas cooler's straight tubes as opposed to conventional synthesis gas coolers with helical tubes: (1) Heat transfer - higher heat transfer rates are achieved due to less contamination; (2) Contamination - the speed of the hot gases through the pipes results in a reduced tendency for contamination; straight pipes allow mechanical cleaning; (3) Pressure drop - lower pressure drop as a result of fewer bends and reduced possibility of clogging; (4) Costs - lower production costs as a result of a less complicated construction.

The gas flow that leaves the main cooling zone can be used as synthesis gas, reducing gas or combustion gas. Alternatively, the remaining free heat in the gas stream can be extracted in one or more preheaters etc., i.e. heat exchangers when preheating boiler feed water. Additional accompanying particulate material can then be removed from the gas stream by washing the gas stream with water in a carbon scrubber. In this way, the concentration of accompanying solids can be further reduced to less than 2 mg/m. The clean gas stream leaving the scrubber saturated with water can then be dewatered. The gas flow is then cooled to below the dew point by indirect heat exchange with boiler feed water or clean fuel gas. Condensed water is separated from the gas stream in a condensation trap ("knockout drum"). The condensate, which is optionally mixed with supplementary water, is returned to the carbon scrubber for use as detergent in the final stage. The clean gas stream that exits at the top of the separator drum has a temperature in the range 93-315 'C, e.g. 135-204 °C, preferably approx. 171 °C. A part of this clean gas flow in the order of 0 to 80% by volume, e.g. 30-60 vol-%, preferably 50 vol-%, can be compressed to a higher pressure than that present in the antechamber. The compressed gas stream can be recycled to the antechamber where it is introduced into the lower extinguishing chamber as the aforementioned recycled gas. The remainder of the cooled, clean gas stream is removed from the top of the separation drum as a gas product.

When a tapped gas stream is used in the gas diversion chamber, it is also cooled and cleaned in the gas washing zone along with the main gas stream. The tapped gas stream that has been separated from the main gas stream in the gas diversion chamber is directed through the gas diversion chamber and then through a communicating, submerged pipe, which exits underwater. This means that the drained gas stream and separated molten slag and/or solid particles are cooled in a water pond at the bottom of the quenching chamber. The water here can have a temperature in the range 10-315 °C. If desired, the hot cooling water on its way to a carbon recovery device can be used to preheat one or more of the feed streams to the gas generator by indirect heat exchange. The tapped gas stream will, after cooling, have a temperature in the range 93-315° C.

The exhaust gas stream leaving the partial oxidation gas generator has

the following composition in mol%: H2 8.0-60.0, CO 8.0-70.0, CO2 1.0-50.0, H20 2.0-50.0, CH4 0-30.0, H2S 0.0-2.0,. COS 0.0-1.0, N2 0.0-85.0 and A 0.0-2.0. The exhaust gas stream contains 0.5-20% carbon by weight in particulate form (basic carbon weight in material added to the gas generator). Molten slag from fusion of the coal's ash content and/or fly ash, particles of refractory material from the walls of the gas generator and other solid particles can also accompany the gas stream leaving the generator.

By means of the method according to the invention, the following advantages are achieved: (1) 90-99% by weight of the accompanying molten slag and/or other particulate material in the hot, fresh gas stream leaving the partial oxidation gas generator can be removed. (2) Essentially all free heat in the hot fresh gas stream leaving the gas generator is utilized, so that the heat efficiency of the process is increased. (3) Steam is produced as a by-product and at a high temperature level. The steam can be used elsewhere in the process, i.e. for heating, for power generation or in the gas generator. Alternatively, part of the by-product steam can be diverted to other uses. (4) Molten slag and/or particulate matter from the solid, carbonaceous fuel can be easily removed upstream of the gas cooler. Contamination of heat exchanger surfaces is thereby prevented. (5) One or more relatively inexpensive shell-and-tube gas coolers with straight flues are used. The construction of such gas coolers makes it possible to distribute thermal stresses equally over the tube plates, it simplifies cleaning and maintenance of the tubes and reduces the ground plan area and height to a minimum.

In the following, reference is made in particular to the drawing, where fig. 1 shows an apparatus according to the invention for extinguishing, cooling and cleaning a hot fresh gas stream containing solid particles and slag. Fig. 2 and 3 show two respective installations, where such a device is used. Similar components in the facilities in fig. 2 and 3 are given the same reference number.

In fig. 2 and 3, a slurry comprising a diameter of 6.35 of bituminous coal in water with a solids content of 40% by weight is pumped in a line 1, by means of pump 2 through line 3 to heat exchanger 4. The temperature of the coal slurry is increased in the heat exchanger 4 from room temperature to 93'C by indirect heat exchange with extinguishing water. The extinguishing water enters the heat exchanger 4 through line 5 and exits through line 6 after giving off heat to the coal slurry. The heated coal slurry is then led through the line 7 and to the annular passage 8 in the burner 9. The burner is mounted in the upper inlet 10 of the synthesis gas generator 11. At the same time, a stream of gas containing free oxygen, e.g. essentially pure oxygen from the line 12, heated by indirect heat exchange with steam in the heat exchanger 13 and led to the gas generator 11 via the line 14 and the central line 15 in the burner 9.

The synthesis gas generator 11 is a steel pressure vessel for free flow and comprises the following main sections: reaction zone 16, gas diversion chamber 17 and extinguishing chamber 18. Reaction zone 16 and the gas diversion chamber 17 are lined on the inside with a heat-resistant refractory material. Alternatively, these three sections may comprise two or more separate and connected and communicating units.

The vertical center axis of the upper inlet 10 runs in line with the vertical center axis of the gas generator 11. The reaction component streams bounce against each other and a partial oxidation takes place in reaction zone 16. A hot fresh gas stream containing accompanying molten slag and/or particulate material, including unconverted carbon and particles of the refractory material, pass through the opening 19, which lies in line with the central axis and is located at the bottom of the reaction zone 16, and enters an enlarged gas diversion chamber 17. The speed and direction of the hot gas flow changes abruptly in the diversion chamber 17. A small part , i.e. a draining stream of the fresh gas is, if desired, drained through the bottom neck 20 in the gas diversion chamber 17, the downpipe 21 and in the water 22 present at the bottom of the quenching chamber 18. In this way, the outlet 20 is kept open, a part of the molten slag and/or particulate material is rapidly cooled and the slag can solidify. Periodically, solid particles and ash are removed from the extinguishing chamber 18 via a lower outlet 23 which is coaxial, line 24, valve 25, line 26, a sluice funnel 27, line 28, valve 29 and line 30. Ash and other solids are separated from the extinguishing water by using the ash conveyor 31 and sump 32. The ash is removed through line 33 for use as filler. Extinguishing water is removed from the sump through line 34, pump 35 and line 36 and can be recycled to the extinguishing chamber. Part of the extinguishing water is removed from the bottom of the extinguishing chamber through the outlet 37 and is led through the line 5 to the heat exchanger 4, as previously discussed. The cooled extinguishing water containing carbon in line 6 goes to a non-conventional carbon separation device for return of extinguishing water via line 38. The recovered carbon is then added to the coal slurry as part of the material fed to the gas generator. Any drained gas is removed from the extinguishing chamber 18 through the side outlet 39, line 40, valve 41 and line 42.

The hot fresh gas stream leaving the diverter chamber 17 with some molten slag and/or particulate material removed is diverted through the side outlet passage 43 which is lined with refractory material and is then led up through a transfer line 44 which is lined with refractory material and an inlet 45 to the antechamber 46, which shown in more detail in fig. 1. In some embodiments, hot fresh gas flow can alternatively be led through a device for the preliminary removal of solids and slag. This device 11A can e.g. be a conventional particle trap. The gas flow then goes to the inlet 45, as schematically shown in fig. 1. The pre-chamber 46 is a closed, cylindrical, vertical steel pressure vessel which is lined on the inside with refractory material 47 and comprises coaxial zones in the form of a lower solid f-f race separation chamber 48, an upper solid f-f race separation chamber 49 and a refractory throat ring 50. Throttle ring 50 forms a cylindrical passage of reduced diameter between lower chamber 48 and upper chamber 49. The antechamber 46 has a conical bottom 51, which converges to a coaxial bottom outlet 52, which is lined with refractory material. The hemispherical dome 53 at the top of the container 46 is provided with an upper outlet 54, which is also lined with refractory material. The outlet 54 is coaxial with the vertical axis of the container 46. A pair of refractory-lined, opposite, coaxial inlet nozzles 45 and 55 extend through the retaining wall and are directed into the lower chamber 48. The longitudinal axis of the inlet nozzles 45 and 55 forms an angle of size approx. 30° and 150° with and measured in the clockwise direction from the vertical center axis of the container 46 and lie in the same plane. Preferred examples of said angle are approx. 45° and approx. 60°. The inlet nozzle 45 points upwards for the inlet of a hot fresh gas flow. The inlet nozzle 55 points down and supplies a stream of clean and relatively colder recycled extinguishing gas. Although only one pair of inlet nozzles is shown in the drawing, further pairs of nozzles can be arranged in the apparatus.

In the preferred embodiment, at least one cyclone 56 is supported in the upper chamber with its vertical longitudinal axis running parallel or coaxial with the vertical axis of the container 46. Each cyclone is resistant to heat and wear and has a gas inlet 57 near the top of the upper chamber. When several cyclones are used, they can be arranged at regular intervals in the chamber. The front of the rectangular inlet 57 of the cyclone 56 is preferably parallel to the vertical axis of the container 46. The inlet is oriented so that it faces the incoming gas flow. The cyclone's inlet can be oriented so that the vortex direction continues.

The cyclone 56 is conventionally constructed and comprises a cylindrical body, a converging, conically shaped bottom portion, a diversion chamber, an outlet plenum communicating with an upper outlet 54, a downcomer 58 and a non-return valve near the lower end of the downcomer. The downpipe 58 can be offset, so that it runs close to the walls of the container 46 and thus does not intersect the common longitudinal axis of the inlets 45 and 55. In this way, contact and build-up of uncooled slag particles on the downpipe is avoided. Cooled, clean synthesis gas is discharged through upper outlet 54. Solid particles are discharged through bottom outlet 52 via line 59, valve 60 and line 61 and pass to a sluice funnel, not shown.

From 1 to 4 tangential extinguishing gas inlets 62 can be evenly distributed around the circumference of the container 46, e.g. near the top of lower chamber 48 and/or near the bottom of upper chamber 49. In this way, a supplemental amount of cooled, clean, recycled extinguishing gas can, if desired, be introduced to container 46. The clockwise helical direction of the recycled gas flow helps to direct all gases in the container upwards. It also maintains a cooler gas flow along the container 46 wall, which protects the refractory lining. The cooled, recycled gas stream which can be introduced through inlet 55 and optionally through the tangential inlets 62, contains at least a part of the cooled, clean gas stream from line 63.

If it is desired to further reduce the solids concentration or the size of the particulate material in the gas stream leaving the antechamber 46 via the upper outlet 54, the gas stream in the conduit 64 may optionally be directed to a conventional solids separation zone 64A, which may be located outside the antechamber 46. Cyclones, bounce separators, bag filters, electrostatic precipitators or combinations thereof may be used for this purpose. They are arranged downstream of the pre-chamber and in front of the main gas cooler.

In the design example according to fig. 2, most of the free heat in the gas stream leaving the pre-chamber is removed in the main gas cooling zone, which in the preferred embodiment comprises two vertically arranged shell-and-tube heat exchangers 65 and 66 with straight flue pipes, where the heat exchangers are connected in series. Both gas coolers 65 and 66 have fixed tube plates, i.e. a lower tube plate 67 and an upper tube plate 68. Although both gas coolers 65, 66 have one passage on the casing side, the gas cooler 65 has one passage on the tube side and the gas cooler 66 two passages on the tube side.

The hot gas stream from the pre-chamber 45, or possibly from a supplementary solids cooling device (not shown) which is arranged downstream of the pre-chamber 45, is cooled by being led up through a lower inlet nozzle 69 to the refractory-lined, fixed bottom cover 70, past the lower, fixed tube plate 67 . gas cooler 66. Central guide plates 77 divide the fixed top cover 76 into a left side 75 and a right side 78. The gas flow on the left side 75 is led by the upper fixed tube plate 68 down through the left set of parallel, straight tubes 79 through the lower fixed tube plate, to the bottom casing 80, up through the right set of parallel, straight vertical tubes 81 to the right part 78 of the top casing 76 and out through the top casing outlet nozzles 82 and line 83. Solids f particles that fall into the bottom mantles 70 h.v. 80 for the gas coolers 65 and 66, are removed via the bottom outlets, as is the flanged nozzle 84 for gas cooler 66. A suitable arrangement for introducing a coolant, in the present case boiler feed water, into each of the two gas coolers 65 and 66 is shown in the drawing. Steam as a by-product is produced in the gas coolers 65 and 66 and is collected in the steam drum 90. Boiler feed water from the drum 90 is led through the line 91 and the inlet nozzle 92 to the jacket side of the gas cooler 65. Steam is removed from the gas cooler 65 through the outlet nozzle 93 and is led to the steam drum 90 via the line 94. in the same way, boiler feed water is led from the steam drum 90 via the line 95 and the inlet nozzle 96 to the jacket side of the gas cooler 66. Steam is removed from the gas cooler 66 through the outlet nozzle 97, and is led to the steam drum 90 via the line 98. Preheated boiler feed water is led to the steam drum 90 through the line 99. Saturated steam is removed from the steam drum 90 through the line 100. This steam can be used in the process, e.g. as a heating medium in the heat exchanger 13 or as a temperature moderator in the gas generator 11 or as a working fluid in a not shown steam turbine for the production of mechanical and/or electrical power. Alternatively, the saturated steam can be superheated.

Further accompanying solid particles and free heat are removed from the gas stream leaving the second gas cooler via the outlet 82 and line 83 by passing the gas stream through the device 101, the line 102 and to the carbon scrubber 103.

In the embodiment shown in fig. 3, most of the free heat in the gas stream leaving the pre-chamber is removed in the main gas cooling zone, which in the preferred embodiment comprises three vertically arranged shell-and-tube heat exchangers 65, 66 and 67 with straight smoke pipes. The three gas coolers have fixed tube plates, i.e. upper tube plates 68 and lower tube plates 69. While the gas coolers 65 and 66 have a passage on the tube side and one on the jacket side.

The hot gas stream from the pre-chamber 56 or, if desired, from a not shown supplementary device for separating solid particles downstream of the pre-chamber 46, is cooled by being led up through the line 64 and the lower inlet nozzle 70 of the gas cooler 65 to the refractory lined hood 71 with stationary head, past the lower fixed tube plate 69, through the tube bundle 72, which comprises a number of parallel, straight, vertical tubes arranged in the jacket 73, past the upper fixed tube plate 68, into the upper hood 74 with stationary head, through the upper outlet 75 and line 76. The coolant in the gas cooler 65 is boiler feed water and saturated steam. The boiler feed water in the steam drum 77 is pumped by the pump 78 through the lines 79-81 and through the lower inlet 82 to the casing side of the gas cooler 65. Saturated steam leaves the jacket side of the gas cooler 65 through the upper outlet 83 and passes to the steam drum 77 via the line 84. At least part of the saturated steam leaves the steam drum 77 through the line 85 and is led to the gas cooler 66 as coolant via the line 86 and the inlet 87. The rest of the saturated steam that may be present is led through line 88, valve 89 and line 90. This steam can be advantageously used in the process or elsewhere. Part of this steam can e.g. is used as a heating medium in the heat exchanger 13.

Most of the partially cooled stream in the line 76 is led to the vertical gas cooler 66 as heating medium for superheating saturated steam by indirect heat exchange. The gas enters via the line 91, the valve 92, the line 93 and the upper inlet 94 to the upper hood 95. The gas is then led on the tube side through the upper tube plate 68, down through the bundle of straight, parallel tubes 96 in the jacket 97, past the lower plate 69, through the lower hood 98 and out through the lower outlet 99 and line 100. Saturated steam in the line 86 is led through the inlet 87 for the gas cooler 66 and then up the mantle side. The by-product superheated steam is removed through the upper outlet 461, lines 462, 463, valve 464 and line 465. The superheated steam can be used in the process, e.g. as working fluid in an expansion turbine for the production of mechanical or electrical power. In another embodiment, at least part of the superheated steam in line 462 is led through line 166, valve 167 and line 168 to the externally heated heating device 169 where the temperature of the superheated steam supply is increased. The by-product superheated steam at a higher temperature level leaves the heater 169 through lines 170 and 171. The superheated temperature of the steam can be controlled by injecting water through line 172, valve one 173 and line 174.

In an exemplary embodiment, the gas flow leaving the gas cooler 65 is used as a fine adjustment to increase the temperature of the gas flow leaving the gas cooler 66 through line 100. This can be achieved by passing a small portion of the gas flow in line 76, through line 175, valve 176, line 177 and that the two gas flows are mixed in line 178.

Additional saturated steam can be produced in the gas cooler 67 by directing the gas flow in line 178 through line 179, the lower inlet 180 to the left side 181 of the lower hood 182, up past the lower fixed tube plate 69, up through the left passage on the tube side 183 , into the hood 184, down through the right passage on the tube side 185, to the right side 186 of the lower hood 182 and out through the lower outlet 187 and line 188. The gas flow passes in indirect heat exchange with part of the boiler feedwater in line 80 from the steam drum 77 .The boiler feed water is led through line 200, valve 201, line 202 and the lower inlet 203 to the one-pass jacket side of the gas cooler 67. Saturated steam leaves the gas cooler 67 through the upper outlet 204 and is passed through line 205 to the steam drum 77.

Solid particles that fall into the lower hood 71, 98 respectively. 182 for the gas coolers 65, 66, respectively. 67, can be removed via bottom outlet, such as the flanged outlet 206 for the gas cooler 67.

An emergency gas injection system is arranged to control the temperature of the gas stream entering the gas coolers 66 and 67. The temperature of the gas stream entering the gas cooler 66 through the line 93 is thus measured and a temperature transmitter signals the temperature control device 190 to open the valve 191 , which controls the amount of steam from lines el92 and 193 required for cooling the gas stream from line 76.

In a similar way, the temperature of the gas stream entering the gas cooler 67 through the line 179 is measured and a temperature transmitter signals the temperature control device 194 to open the valve 195, which controls the amount of steam from the lines 196 and 197 which is necessary for cooling the gas stream from the line 178. The steam for operating the emergency system for steam injection can advantageously be produced in-house.

Additional accompanying solids and free heat are removed from the gas stream leaving the gas cooler 167 by means of the outlet 187 and line 188, by passing the gas stream through a device 101 that utilizes waste heat, the line 102 and to the carbon cleaner 103.

In both embodiments, the carbon cleaner 103 comprises a vertical container with two compartments, i.e. an upper chamber 104 and a lower chamber 105. The gas stream in the line 102 passes through the inlet 106 to the lower chamber 105 and then through the submerged pipe 107 to the water bath 108 at the bottom of the lower chamber 105. The washed gas stream leaves the lower chamber 105 via the outlet 109 and goes via the lines 110 and 111 to the venturi washer 112. There the gas stream is washed with water from the line 116. The gas stream that has been washed in the venturi washer 112 is led to the upper chamber 104 via the line 117 and the inlet 118. Via the submerged pipe 119 the gas stream becomes then led to and washed in the water bath 120. Before the gas flow leaves the upper chamber 104 via the upper outlet 121 at the top of the chamber 78, it can be given one more flush by means of a water spray 122 or by means of a washing trough not shown. The condensate 123 from the bottom of the ejection drum 124 can e.g. is led through the line 125 and introduced through the inlet 126 into the spray 122. Water from the bath 120 is led through the line 127, the outlet 128, the line 129, the pump 130, the lines 131 and 132, the inlet 133 and the pipe 134 to the extinguishing chamber 18. Part of the water in line 131 can be recirculated to the lower chamber 105 in the gas scrubber 103 via line 135, valve 136, lines 137 and 138 and inlet 139. Another part of the water in line 137 goes via line 140 and is mixed in line 116 with supplementary water from the lines 141, the valve 142 and the line 143. The water in the line 116 is led to a venturi 112 as previously mentioned. The water containing dispersed solid particles 108 from the bottom of the chamber 105 is passed through the outlet 144, the line 145, the valve 146, the line 147 and is mixed in the line 38 with the water dispersion from the line 6. The water dispersion in the line 38 goes to a conventional, not shown, carbon recovery device, where water is separated from the accompanying solid particles. The reclaimed water is returned to the device as make-up water. The make-up water can be brought in at different places, e.g. through line 141, as discussed above.

The purified gas stream that leaves the upper chamber 104 in the carbon washing device 103 via the upper outlet 121 and the line 155 is led through the device 156 for the recovery of waste heat and where it is cooled below the dew point. The wet gas stream passes through line 157 to the ejection drum 124, where separation of condensed water from the gas stream takes place. A cooled and purified stream of product gas leaves the top of the drum 124 via lines 158 and 159. If desired and advantageously, if the gasifier 11 is operated according to the slag formation method, a portion of this cooled and purified product gas is sent through line 160, valve 161, line 162 , the gas compressor 163 and then recycled as extinguishing gas stream to the lower chamber 48 in the antechamber 46 via the line 63 and the inlet passage 55 and optionally through the tangential gas inlet 62.

Supplementary boiler feed water for cooling the shell-and-tube heat exchangers with straight smoke pipes (65, 66) is preheated by being led through line 164, device 156, as coolant, line 165, device 101 as

refrigerant, the line 99 oe to h- .

™-< advantage, to LmZ 65 T~n Deffra kje'~te-05 and 66, as discussed above.

Claims (26)

1. Process for cooling and purifying a hot gas stream, produced by partial oxidation of an ash-containing, solid, carbonaceous fuel, where 1) particles of the solid fuel are caused to react with a gas containing free oxygen, with or without a temperature moderator in a refractory-lined gas generator (11) with downward flow at a temperature in the range 925-1705° C and a pressure in the range 10-299 atm for producing a fresh gas stream containing H2, CO, CO2 and at least one material from the group comprising H2O, H2S, CO S, CH4, NH3, N2 and A and which contains molten slag and/or particulate material, characterized in that 2) the fresh gas stream is directed through a heat-insulated transfer line (44) and a first gas inlet (45) to a lower chamber (48) in a gas-solid separation zone comprising a closed, vertical, cylindrical, heat-insulated pressure vessel (46), containing said lower chamber (48) which is coaxial with the vertical central axis of the pressure vessel and communicates with a coaxial upper chamber (49), where the lower and upper chambers are connected by a coaxial throat ring passage and where part of the slag and/or particulate material is precipitated by by gravity and falls to the bottom (51) of the lower chamber (48), 3) the gas mixture is led from the lower chamber (48) up through the throat ring (50) to the upper chamber (49) in countercurrent with slag droplets and then optionally to a gas-solid separation device (56) which is placed in the upper chamber, 4) slag and/or particulate material is separated from the gas mixture in the upper chamber (49) and removed from the container via an outlet (52) in the bottom of the lower chamber, and 5) purified gas is removed from the upper chamber (49) and emptied through an outlet (54) at the top of the vertical container. 2. Method as stated in claim 1, characterized by the additional step that at the same time an oppositely directed flow of cooled and purified recirculation gas is led through a second gas inlet (55), which runs coaxially with the first gas inlet (45), into the lower chamber, where the induces a turbulent mixture of gases, when the two gas streams bounce against each other, where molten slag accompanying the hot gas stream is cooled below the temperature at which the slag begins to deform, falls out as a result of gravity and falls to the bottom in the lower chamber (48). 3. Method as stated in claim 2, characterized by the further step that a part of the purified gas stream from step 5) after further cooling and possibly after further purification is introduced downstream into the lower chamber in step 2) as at least part of said recirculation gas. 4. Method as stated in claim 2 or 3, characterized in that the hot gas stream and the cooled and purified recirculation gas stream in step 2) are introduced into the lower chamber through a number of pairs of first and second coaxial opposite inlets whose longitudinal axis lies in the same plane as the container's vertical central axis and forms an angle in the range of 30° to 150° with the vertical central axis, measured clockwise from the latter. 5. Method as stated in one of claims 2-4, characterized by the further step that the clean recycled gas flow is compressed to a higher pressure than the pressure in the lower chamber before said gas flow is introduced into the lower chamber in step 2). 6. Method as stated in one of the preceding claims, characterized by the further step that part of the cooled and purified gas stream is introduced at the top of the lower chamber and/or at the bottom of the upper chamber via tangential inlets (62). 7. Method as stated in one of the preceding claims, characterized in that an upper chamber is used in the gas-solid separation zone in step 2) which is provided with at least one gas-solid separation device (56) selected from the group comprising one-stage and multi-stage cyclones, gas bounce separators, filters and combinations thereof. 8. Method as stated in one of the preceding claims, characterized in that additional solids are removed from the purified gas stream from step 5) in a second gas-solids separation zone (64A) which is located downstream of said gas-solids separation zone and comprises separators from the group a -stage and multi-stage cyclones, bounce separators, filters, electrostatic separators and combinations thereof. 9. Method as stated in one of the preceding claims, characterized by the additional steps that the fresh gas flow from step 1) is sent down through the central outlet at the bottom of the reaction zone and to a heat-insulated diversion chamber, which is provided with a side outlet and a bottom outlet, that the molten slag and/or particulate material is separated from the gas stream by means of gravity, that from 0 to 20% by volume of the gas stream is led as drained gas together with the separated material through the bottom outlet of the diversion chamber and to a slag chamber located below the diversion chamber, while the rest of the gas stream is led through a side outlet in the diversion chamber directly to the heat-insulated transmission line. 10. Method as stated in one of the preceding claims, characterized by the further step that part of the purified gas flow from step 5) is introduced into a gas cooler in indirect heat exchange with H2O and produces steam. 11. Method as stated in one of the preceding claims, characterized by the additional steps that the gas flow from step 5) is cooled in a main gas cooling zone (65, 66) and produces steam as a by-product by the gas flow being conducted in indirect heat exchange with preheated boiler feed water, first up through the pipes for a vertical shell-and-tube gas cooler (65) for high temperatures and with straight smoke pipes, which have refractory-lined inlet and outlet sections, a passage on the shell and tube sides and fixed tube plates, the gas flow is then directed down through the pipes in the first passage on the pipe side of a vertical shell-and-tube gas cooler (66) for lower temperatures and with straight smoke pipes, which has two passages on the pipe side and one passage on the shell side and has fixed tube plates, and that the gas flow is then led up through the pipes in the second sweep on the pipe side of the second gas cooler, and that steam as a by-product is removed from the jacket sides of the first and second gas cooler. 12. Method as stated in claim 11, characterized by the further step that the boiler feed water is preheated by indirect heat exchange with the gas flow (83) leaving the second gas cooler. 13. Method as stated in claim 12, characterized in that the cooled gas stream is washed with water in the gas-washing zone (103) and produces a carbon-water dispersion (145), that at least part (6) of this carbon-water dispersion is mixed with or without concentration and addition of solid fuel to produce a slurry of solid fuel, that this solid slurry is preheated and gasified in the gas generator in step 1). 14. Method as set forth in claim 11, characterized by the steps that simultaneously separate portions of preheated boiler feed water are led from a steam drum (77) through the jacket side of the gas coolers for high h.v. lower temperature and that the steam thus produced is led to the steam drum, and that saturated steam as a by-product is removed from the steam drum. 15. Method as stated in one of the claims 1-9, characterized by the further steps that the gas flow from step (5) is cooled in a main gas cooling zone (65, 66, 67) and produces saturated and superheated steam as a by-product by the gas flow being directed in indirect heat exchange with preheated boiler feed water, first up through the pipes in a first vertical high-temperature jacket-tube gas cooler (65) with straight smoke pipes and with refractory-lined inlet and outlet sections, one sweep on the tube and jacket sides and fixed tube plates, on which the gas flow is directed in indirect heat exchange with saturated steam down through the tubes in a second vertical shell-tube gas cooler (66) with straight smoke tubes, which has a sweep on the tube side and the shell side and has fixed tube plates, whereupon the gas flow is led in indirect heat exchange with preheated boiler feed water up through the tubes in the first tube-side sweep of a third gas cooler (67) comprising a vertical low-temperature mantle-tube gas cooler with straight flues with two tube-side sweeps and one mantle sweep side and with fixed tube plates, and then down through the tubes in a second sweep on the tube side for said third gas cooler, that saturated steam is produced on the jacket sides of the first and third gas coolers and that at least part of the saturated steam is superheated on the jacket side of the second gas cooler for the production of superheated steam as a by-product, while the remainder, if any, is removed as a saturated steam by-product, and that the boiler feed water which is preheated by indirect heat exchange with the gas stream leaving the third gas cooler. 16. Method as stated in claim 15, characterized by the steps that simultaneously separate portions of preheated boiler feed water are led from a steam drum (77) through the jacket sides of the first and third gas coolers and that the steam produced thereby is led to the steam drum, and that at least one part of the saturated steam (85) from the steam drum is led to the jacket side of the second gas cooler. 17. Method as stated in claim 15, character, in that 0-50% by volume of the gas stream (76) leaving the first gas cooler is led past the second gas cooler and mixed with the gas stream (100) leaving the second gas cooler. 18. Apparatus for carrying out the method according to claim 1 for cooling and cleaning a hot gas stream produced by partial oxidation of solid, carbonaceous fuel, characterized in that it comprises 1) a partial oxidation gas generator (11) for the production of the hot gas flow, 2) a separate, closed, vertical, cylindrical pressure vessel (46), which is internally lined with refractory material with high resistance against high temperatures, with a coaxial lower gas-gas quench cooling and solid f-separation chamber (48) in communication with a coaxial upper chamber (49), a reduced-diameter coaxial throttle passage (50) connecting the lower and upper chambers, 3) a first gas inlet nozzle (45) which is connected to the gas generator (11, 11a) for introducing the hot fresh gas stream into the lower chamber, a second gas inlet nozzle (55) directly opposite and coaxial with the first gas inlet nozzle (45) for simultaneous introduction of a cooled and purified gas stream in the lower chamber, arranged so that the two gas streams bounce against each other, 4) upper outlet means (47, 54) in the upper part of the upper chamber (49) for emptying a cooled and purified gas stream and 5) a bottom outlet (52) at the bottom of the lower chamber for emptying solids and slag (59). 19. Apparatus as stated in claim 18, characterized in that it further comprises at least one gas-solids separation device which is supported in the upper chamber to receive the gas mixture which, during use, passes up into the container from step 3) and to remove further solids from the gas mixture and empty these solids into the lower chamber. 20. Apparatus as stated in claim 19, characterized in that the gas-solid separation device is a one-stage or multi-stage cyclone separator or a bounce separator or a filter or a combination of these. 21. Apparatus as stated in one of claims 18-20, characterized in that it comprises a gas-solids separation device outside and downstream of the container for separating further solids from the gas stream from step 4). 22. Apparatus as stated in claim 21, characterized in that the gas-solid separation device outside the container is a one-stage cyclone separator, or a multi-stage cyclone separator or a bounce separator or an electrostatic precipitator or a filter and/or combinations thereof. 23. Apparatus as specified in one of claims 18-22, characterized by several pairs of first gas inlets and coaxial second gas inlets in stage 3). 24. Apparatus as specified in one of the claims 18-20, characterized by at least one tangential inlet which is arranged in the upper part of the lower chamber (48) or in the lower part of the upper chamber (49) or both places for supplying a portion cleaned and cooled , recycled gas stream. 25. Apparatus as stated in one of claims 18-21, characterized in that there are arranged organs for supplying the cooled and purified gas stream in stage 3), in the form of at least part of the cooled and purified gas stream from stage 4) with further cooling and with or without further cleaning downstream of the pressure vessel. 26. Apparatus as stated in one of claims 18-25, characterized by a preliminary solids and slag removal device which is connected between the outlet from the gas generator in stage i) and the inlet to the first gas inlet nozzle in stage 3).