GB2038867A

GB2038867A - Watergas Reactors

Info

Publication number: GB2038867A
Application number: GB7933681A
Authority: GB
Original assignee: Brennstoffinstitut Freiberg
Current assignee: Brennstoffinstitut Freiberg
Priority date: 1978-09-28
Filing date: 1979-09-28
Publication date: 1980-07-30
Also published as: FR2437434B1; HU181856B; GB2038867B; DE2935989A1; PL117620B1; ATA635379A; AU5114679A; CS220584B1; PL218606A1; DD145181A3; AU527929B2; YU235579A; FR2437434A1; IN154344B; JPS5844716B2; JPS5647487A

Abstract

A reactor for the production of gases containing CO and H2 by partial oxidation of liquid fuels or fuels in the form of dust, especially fuels with an ash content, using a gasification medium containing free oxygen, the process being effected at high temperatures and elevated pressure. In such a process the pressure jacket of the reactor must be reliably shielded from overheating and the effect of the crude gas and have a long life. This is achieved in that the wall of the reactor chamber (4) is formed from tubing (7) and surrounded by a gastight housing (8) which in turn is accommodated inside an outer pressure vessel (1). The gap between the housing (8) and the tubes (7) of the coil is filled in with a refractory clay material (19). Webs (16) secured to the inside of the housing divide this into a plurality of sections. The reaction chamber is connected to a space (11) between outer pressure vessel and housing by one or more openings (12, 13). The supply of an inert flushing gas is effected through at least one socket (22) to the space (11). <IMAGE>

Description

SPECIFICATION Reactor for the Production of Gas by Partial Oxidation This invention relates to a reactor for the production of gases containing CO and H2 by partial oxidation of liquid fuels or fuels in the form of dust, particularly fuels containing ash with a gasification medium containing free oxygen at high temperatures and elevated pressure.

In the production of gas from liquid fuels or fuels in the form of dust by partial oxidation, the fuel reacts with a gasification medium containing oxygen in a flame reaction. Depending on the fuel and the field of use for the gas, final temperatures of the reaction between 1 200 and 1 6000C occur, while in the flame itself temperatures above 20000C are reached. If fuels containing ash are used, the mineral residues of the partial oxidation process occur in a molten state.

The flame reaction takes place in a refractory, generally axially symmetrical reaction chamber, the known methods differing in the arrangement of the burners and the removal of the hot crude gas produced and the slag.

Gas producing processes of such a kind are frequently operated at elevated pressure, for example at 3 MPa. Reactors for such a pressure consist, for example, of an outer pressure vessel in the interior of which is the actual reaction chamber formed by walls of water-cooled tubes.

The tube walls are provided at the side adjacent to the flame with a layer of refractory tamping clay, for example a silicon carbide material. The adhesion of the tamping clay to the tubes is achieved by pins for example 10 mm in diameter and 10 mm high, which are welded to the tube surface and project into the layer of tamping clay.

The thickness of the layer of tamping clay is such that the surface temperature is lower than the solidifying temperature of the slag occurring during the partial oxidation process. During the operation of the reactor, therefore, a further layer of solidified slag forms on the surface of the tamping clay and merges into a pasty zone and finally into a molten film of slag running away.

The cooling of the tube wall can be effected with pressurised water at a temperature below the boiling point or with steam.

The tube wall must reliably protect the outer pressure jacket from overheating by radiation and convention flow. A thermal insulating layer of refractory material is therefore often provided between tube wall and outer pressure jacket.

Through joints in the brickwork and expansion joints, through inevitable cracks and through the porosity of the refractory material, this insulating layer inevitably has a considerably permeability to gas which cannot be locally defined. If the reactor is ignited at substantially atmospheric pressure, as usual, and brought to the full operating pressure in the hot state, with a rapid rise in pressure such large vagrant streams of gas may occur that the pressure jacket is locally overheated. The same risks are to be expected when major pressure differences appear inside the reaction chamber or in the crude gas outlet passage through high performances and through partial slagging.

As a rule, although the cooled tube wall can be operated at temperatures above the condensation point of water vapour, nevertheless the temperature of the pressure jacket remains below this point. The permeability of the insulating layer to gas renders possible the condensation of steam on the pressure jacket and favours corrosion.

It has been proposed to flush the brickwork or defined joints in the brickwork with inert gases.

The permeability of the brickwork to gas cannot be defined, locally at least, and this restricts the effect of such a measure to a minimum even with large amounts of flushing gas. Embodiments of reactors with cooled tube wall constructions are known wherein the individual tubes disposed side by side are connected by welded-in webs extending over the whole tube length. Thus the tube wall becomes gastight. The communication between the reaction chamber and the space between tube wall and pressure jacket, necessary for pressure equalization, is restricted to one or a few controllable openings, which can be effectively mastered by flushing with inert gas.

Such a solution leads to a very rigid tube wall construction, a further advantage of which lies in simpler holding constructions and easier assembly. The rigidity of the tube wall involves the following important disadvantage, however: During starting and stopping operations and on a change of load, the tamping clay and solidified slag cannot be prevented from expanding or shrinking. The rigid, welded tube wall construction cannot follow these changes in length so that the tamping clay frequently peels off the tube wall. The thermal loading of the parts of the tube wall laid bare, which is many times higher, can lead to danger through local overheating.

This invention seeks to provide a reactor for the production of gas by partial oxidation of liquid fuels or fuels in the forms of dust containing ash, under pressure, the pressure jacket of which is protected from overheating and from the action of crude gas and which permits long life, and in which the reaction chamber is formed by a watercooled tube wall construction provided with tamping clay at the reaction chamber side, the outer pressure jacket of which is protected from overheating and the effect of the crude gas atmosphere in all operating phases, the components, particularly the tube wall construction is simple to assemble and disassemble and ensures a long life particularly with regard to the durability of the tamping clay lining in the reaction chamber.

The tube wall forming the reaction chamber, studded at the reaction chamber side and provided with refractory tamping clay is surrounded at a distance of generally 1 to 5 cm by a gastight housing, and the gap between the individual tubes of the tube wall and the housing is likewise filled with refractory tamping clay.

Secured to the inside of the housing are webs which divide this inside into a plurality of sections and which project into the tamping clay. The object of these webs is to prevent large-area streams of hot gas at the housing wall despite the inevitable cracking between tamping clay and inside of the housing in the course of operation.

According to the invention, these webs may also serve to locate the length of the tube wall without a rigid connection being brought about between these webs and the tubes of the tube wall. The housing is accommodated inside an outer pressure vessel.

The space between the wall of the outer pressure vessel and the housing is connected to the reaction chamber inside the housing through one or more openings. One or more inlet possibilities (sockets) for an inert gas are provided on the outer pressure vessel, with which the space between outer pressure vessel and housing can be flushed.

In a preferred form of embodiment of the invention for reactors with an upright cylindrical reaction chamber, the ends of which are provided with axial openings to receive the burner and the crude-gas and slag outlet, the cylindrical part of the tube wall consists of one or more parallel tubes which are wound into a single or multiple coil and the inlet and outlet ends of which for the cooling medium are taken through the housing and via easily detachable, pressuretight ducts of known construction, through the outer pressure vessel. The tubes are studded at the side adjacent to the axis of the coal. According to the invention, one or more webs, which project into the gap between two adjacent tube turns, are secured to the inside of the housing surrounding the tube coil at least in one layer.

According to the invention the length of a web corresponds to one complete turn. The ends of the web are connected by a further web, with a parallel axis, the outer edge of which is adapted to the outer profile of the tube coil, that is to say is provided with one or more semicircular recesses depending on the number of threads in the coil, the radius and spacing of the recesses being adapted to the tube diameter and the spacing of the turns in the coil.

The gap between the tube coil and the inside of the housing and, as is known, the studded side of the tube wall forming the contours of the reaction chamber, is provided with a refractory tamping clay.

According to the invention, the tube wall provided with tamping clay forms a structural unit with the housing, preferably by a weld connection between housing and inlet and outlet ends of the tubes and by positive connection and can be introduced and mounted as a whole in the outer pressure vessel or be removed from the pressure vessel after the pressure tight ducts for the tube ends through the outer pressure vessel have been loosened.

With the solution according to the invention, with suitable dimensioning of the connecting apertures between reaction chamber in the interior of the housing and the gap between the outer pressure vessel and the housing, it is easily possible to adjust the amount of inert flushing gas so that the entry of crude gas into this gap is prevented with the minimum requirements of flushing gas. Only in the phase of the pressure rise in the reaction chamber during the starting process must the amount of inert gas be readjusted depending on the size of the free volume in said gap and the gradient of the pressure rise in the reaction chamber, to such an extent that the rate of flow of the inert gas out of the gap into the interior of the housing always remains greater than zero.

With the solution according to the invention, as a result of dispensing with the rigid connection between the individual tubes or tube turns, adequate resilient deformability of the tube wall remains so that the individual tubes can yield to thermal expansions and shrinkages of the layer of tamping clay covered, in the operational state, with a layer of solidified slag and the risk of the tamping clay peeling off is considerably reduced.

In addition, the solution according to the invention permits a defined flushing of the inner wall of the outer pressure vessel so that thermal and corrosive effects on the jacket of the pressure vessel by the crude gas can be avoided.

The invention will be further described with reference to an embodiment shown by way of example in the accompanying drawings.

Figure 1 shows a diagrammatic illustration in section of a reactor for the partial oxidation of fuels in the form of dust under elevated pressure, Figure 2 shows a detail of the 4 tube coil, and Figure 3 shows a detail in section through the housing, tube coil tamping clay coating and slag layer.

The reactor is designed for a pressure of 3.0 MPa and intended for the gasification of brown coal dust with about a 10% ash content by partial oxidation by means of industrial oxygen. As shown in Figure 1, the reactor has a cylindrical reaction chamber, the ends of which are provided with axial openings to receive the burner and the crude gas offtake, and two-part outer pressure vessel 1, consisting of a pressure vessel body 3 and a cover 2, connected by a flange. In the interior is a reaction chamber 4 in which, at a temperature of about 1 40ooh and at the abovementioned pressure, industrial oxygen and brown coal dust react with one another in a flame to form a gas containing CO and H2.

The supply of the reaction precursors is effected through the burner insert 5 which also carries devices for the ignition and for the temperature measurement in the reaction chamber.

The crude gas produced passes at a temperature of about 1 400CC together with the molten slag into the discharge and cooling device 6, through which it leaves the reactor and after separation of the slag is supplied for further processing.

The reaction chamber is encased by a four tube coil 7 formed from four separate tubes. For the sake of clarity, only part turns of this coil is shown in Figure 1, while Figure 2 shows, in perspective, a detail of the coil formed from the four tubes. The tubes of the coil are provided, at the side adjacent to the reaction chamber, with welded-on pins 23, as Figure 3 shows the arrangement in detail.

The tube coil 7 is encased by a gastight housing 8 which, in comparison with the jacket of the outer pressure vessel, is made of relatively thin sheet metal. The distance between the outside of the tubes forming the coil and the housing amounts to about 2 cm. The housing with the tube coil rests on brackets 9 which support the load at the bottom of the pressure vessel 1.

For the sake of convenient mounting, the housing is also provided with a lifting eye 10 for the attachment of lifting equipment. The gap 11 between housing 8 and the jacket of the outer pressure vessel 1 is connected to the reaction chamber 4 through the annular gap 12 between burner insert 5 and an upper opening in the housing. There is a further connection through the lower annular gap 13 between a lower opening in the housing 8 and the discharge and cooling device 6 for the crude gas, which gap is largely blocked by slag during operation. With the socket 22, the possibility is afforded of flushing the gap 11 with nitrogen which enters the reaction chamber through the openings 12 and 13 in the form of annular gaps.The upper and lower ends 1 5 of the tubes forming the tube coil 7 are taken to the outside through the bottom of the pressure-vessel body 3 and the cover 2 through easily detachable welded ducts 14 and - not illustrated in Figure 1 - are connected to cooling water supply and discharge pipes. The water pressure in the cooling tubes amounts to 4.0 MPa and is higher than the pressure in the reaction chamber. The temperature of the incoming water amounts to 1 600C and is higher than the dew point of the crude gas which is about 1 50 C.

The inside of the housing 8 is provided with a plurality of helical webs 16 made with the same pitch as the tube coil 7 and distributed over the height, which project into the gap between two adjacent tube turns of coil at the height of the tube axis. The length of a web 1 6 corresponds to a complete screw turn. The ends of each web 16, situated vertically one above the other, are connected, as Figure 3 ahows, to a further web 1 7 which is disposed vertically and the outer edge of which is provided with four semicircular excisions 18, the radius and spacing between the turns of the tube coil 7 consisting of four tubes.

The vertical web 1 7 thus engages (like a comb) in the tube coil 7.

The tube coil 7 is embedded in a refractory tamping clay 1 9 with a silicon carbide base which not only fills in the gap 24 between tube coil 7 and wall of the housing 8 but also covers the tube surface directed towards the reaction chamber 4.

The thickness of the layer covering the tubes on the inside is selected at about 20 mm so that the temperature at the surface of the tamping clay 19 is lower than the solidifying temperature of the molten slag which is about 1 000C. When the molten slag arrives on the wall, a solidified layer of slag 20 develops over the refractory tamping clay 19 and ultimately merges into a film of molten slag 21, as Figure 3 shows. In operation, a state of equilibrium develops with regard to the thickness of the layer of solid and molten slag, which state of equilibrium depends on the temperature, the heat transfer conditions and the power of the flame reaction in the reaction chamber 4 on the one hand and on the cooling intensity and heat conduction in the tamping clay 19 and cooling tubes on the other hand.

The tamping clay 19 and solidified layer of slag 20 form a comparatively firm and rigid combination and are subjected to thermal expansions and shrinkages during starting and stopping processes and during alterations in the operating state. With the solution selected, however, there is adequate flexibility of the tube coil 7 so that this can follow the thermal movements of tamping clay and slag. In this manner the risk of tamping clay peeling off is largely reduced. It is inevitable, on the other hand, that in the course of operation, cracks appear between tamping clay 19 and wall of the housing 8. The webs 1 6 projecting into the tamping clay 19 and wall of the housing 8.The webs 16 projecting into the tamping clay 1 9 and vertical webs 17, however, prevent hot gases from flowing in a large area behind the tamping clay 19 so that overheating of the housing 8 cannot occur. Instead, the housing 8 becomes adjusted to a temperature which corresponds substantially to the average coolant temperature in the tube coil 7 (about 1 8O0C). Thus the condensation of water vapour is avoided. The amount of nitrogen supplied to the gap 11 between outer pressure vessel 1 and housing 8 through the socket 22 is so dimensioned, in normal operation, that the velocity in the annular gap 12 and lower annular gap 13 amounts to about 0.2 m/s. Only in operating phases when the pressure in the reaction chamber 4 is increased, the throughput of nitrogen reduced to normal pressure is increased to a value which is somewhat greater than the value asp 1 VZw.

AT z ' p0 in which Vzw is the volume of the gap 11, Ap/AT the pressure rise per unit of time and p0 the normal pressure.

At the jacket of the outer pressure vessel 1 therefore a nitrogen atmosphere prevails internally and the condensation of water vapour out of the crude gas is avoided. In order to restrict the temperature of the outer pressure vessel 1 to values which exclude inconvenience to the operating staff, the inside of the outer pressure vessel 1 is also provided with a thin insulation not illustrated in Figure 1.

Claims

1. A reactor for the partial oxidation of liquid fuels and/or fuels in the form of dust which contain ash, at elevated pressure in which the reaction chamber has a wall formed from tubing and cooled by flow through the tube and covered with a refractory material, the individual turns of the tube or tubes forming the wall being resiliently mounted to be movable in relation to one another, and wherein the tubing is enclosed by a gastight housing which is accommodated within an outer pressure vessel with the gap between the housing and the tubes filled in with a refractory material, webs being secured to the inside of the housing which divide same into a plurality of sections and which project into the refractory material filling the gap, the reaction chamber inside the housing being connected to the gap between outer pressure vessel and housing through one or more openings and the gap between outer pressure vessel and housing being provided with at least one socket for the supply of a non-reactive flushing gas.

2. A reactor as claimed in Claim 1, wherein the cylindrical part of the tubing wall is in the form of a single or multiple tube coil.

3. A reactor as claimed in Claim 1 or 2, wherein on the inside of the housing in one or more layers, one or more webs are secured in helical configuration and with the same pitch as the tubing coil forming the wall, the webs projecting into the gap between two adjacent tube turns.

4. A reactor as claimed in any preceding claim, wherein the length of a web corresponds to a complete turn and the ends are connected by a further web parallel with the reactor axis and secured to the housing, the outer edge of said web comprising one or more semicircular excisions, the radius and spacing of the excisions being adapted to the tube wall.

5. A reactor as claimed in any preceding claim, wherein the tubing wall provided with refractory material and the housing can be introduced for mounting as a structural unit in the outer pressure vessel.

6. A reactor constructed and arranged to function substantially as herein before described with reference to and as shown in the accompanying drawings.