Combination of pressure charging and metering for continuously supplying pulverized fuel into an entrained-flow gasifying reactor with long conveying distances

Abstract

A system for fluidizing and conveying a powdery product is provided. The system includes plurality of powder-locking and metering vessels, the vessels each having a conveying line for the powdery product and a control mechanism for the mass flow of the powdery product. The conveying lines are brought together to form a common conveying line and are supplied to a remover of the powdery product. The powder-locking and metering vessels are alternatively fed with the powdery product and tensioned with the fluidizing gas under operating pressure. The control mechanisms of the powder-locking and metering vessels are activated in such a manner that the mass flow sum of powdery product in the conveying lines is identical to the desired value for the mass flow of powdery product to the remover of the powdery product.

Claims

1. A system for the pneumatic feeding-in of pulverized fuel in which a H2- and CO-rich crude gas is produced by conversion of an entrained-flow gasifying reactor with oxygen or containing free oxygen, comprising: an untreated fuel stored in an untreated fuel silo is supplied to a device below the untreated fuel silo for drying and grinding the fuel to form powdery fuel, a filter, wherein the pulverized fuel is subsequently freed from an entrained drying and circulating gas as the pulverized fuel is passed through the filter, a plurality of combined powder-locking and metering vessels that are discontinuously or cyclically filled with the pulverized fuel and tensioned with fluidizing gas set under operating pressure, wherein the pulverized fuel is set under operating pressure and is introduced in a fluidized state, each of the combined powder-locking and metering vessels convey a defined flow of the fluidized pulverized fuel via an allocated powder-conveying line and an allocated control valve into a common conveying line, the entrained-flow gasifying reactor, wherein in the fluidized state, the pulverized fuel is supplied by continuous conveying through the common conveying line to the entrained-flow gasifying reactor, wherein the fluidized pulverized fuel is supplied continuously to the entrained-flow gasifying reactor by the desired value for mass-flow control of the pulverized fuel divided between the control valves of the powder-conveying lines of the plurality of combined powder-locking and metering vessels, a portion divider that displaces the desired value from a first control valve of the control valves to a second control valve of the control valves, wherein the desired value is displaced via ramping within the portion divider, wherein the time of the ramping is set, wherein the ramping exit out of the portion divider is multiplied by the desired value of the mass flow for the second control valve and, for the first control valve, the ramping exit out of the portion divider is subtracted from 1 and multiplied by the desired value of the mass flow, wherein in parallel to the activation of the control valves, a supply of fluidizing gas of the respective combined powder-locking and metering vessel assigned to the second control valve under fluidizing plates is started and the conveying begin.

2. The system as claimed in claim 1, wherein the mass flow of powdery fuel output by a powder-locking and metering vessel is controllable in accordance with the setting of the respective control valve, which is associated with said combined powder-locking and metering vessel, in the associated conveying line.

3. The system as claimed in claim 1, wherein the mass flow of powdery fuel output by a powder-locking and metering vessel is controllable in accordance with the amount of fluidizing gas set in a fluidizing gas line via the respective control valve associated with said combined powder-locking and metering vessel.

4. The system as claimed in claim 1, wherein the powdery fuel of the common powder-conveying line is dividable by a powder flow divider into a plurality of divided-up conveying lines connecting the divider with the entrained-flow gasifying reactor.

5. The system as claimed in claim 4, wherein that said system is dimensioned in such a manner that the ratio of the cross section of the divided-up conveying lines to the conveying line is 1.5 to 3 times.

6. The system as claimed in claim 1, wherein the diameter of the powder-conveying line is increased over the conveying length, wherein the flow speed is reducible by up to half by expansion of the powder-conveying line.

7. The system as claimed in claim 1, wherein said system is dimensioned in such a manner that the pressure loss in the powder-conveying lines is at maximum 20% of the pressure in the metering vessel.

8. The system as claimed in claim 1, wherein the pulverized fuel is supplied to the powder-locking and metering vessels from the device for drying and grinding.

9. The system as claimed in claim 1, wherein the fluidizing gas is provided by an inert gas.

10. The system as claimed in claim 1, wherein the entrained-flow gasifying reactor converts the pulverized fuel into crude gas.

11. The system as claimed in claim 1, further comprising an auxiliary gas line connected to a powder conveying line.

12. The system as claimed in claim 1, wherein the system is configured for overcoming conveying distances of 80 to 500 m, under an operating pressure of up to 10 MPa.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in more detail below as an exemplary embodiment to an extent required for understanding and with reference to figures, in which:

(2) FIG. 1 shows the interaction according to the invention of essential elements of a coal-grinding and drying plant with the gasifying plant,

(3) FIG. 2 shows a particular solution for large conveying lengths, and

(4) FIG. 3 shows the changing-over from one metering vessel to another metering vessel within a time period of t0 to t1.

DETAILED DESCRIPTION OF INVENTION

(5) In the figures, the same designations denote identical elements.

Example 1

(6) A gasifying plant according to FIG. 1 for producing synthesis gas has a gross capacity of 500 MW. Pulverized fuel is required at 82 Mg/h. For this purpose, the raw coal is passed by raw-coal conveying technology 1 to a raw coal silo 2 and is processed in the two-line drying and grinding plant 3 to form a pulverized fuel with a residual water content of 2.5 Ma % and a 50 Ma % grain size of smaller than 60 m. Said pulverized fuel is separated from drying and circulating gas in the powder filter 4. The powder temperature is 50 C. There are a total of three combined pressure and metering locks 5 (only two are shown) which are fed alternately by gravitational conveying from the powder filters 4 and are tensioned by supply of oxygen-free or low-oxygen gas. As a result, despite the discontinuous filling and tensioning operation of the combined powder-locking and metering vessels, a continuous supply of powder from the powder-conveying lines 6 and the line 14 to the gasifying reactor 7 can be achieved. The tensioning pressure in the pressure and metering locks 5 corresponds to the pressure in the entrained-flow gasifying reactor 7 plus the pressure loss in the powder-conveying lines 6 and 14. The tensioning gases can be provided by nitrogen, carbon dioxide, low-oxygen exhaust gases, but also combustible gases, such as natural gas or residual gases from the entire process. The combined powder-locking and metering vessel 5 can be tensioned, for example, with the fluidizing gas 16 which is supplied below the fluidizing plate 15. In this case, the pulverized fuel is already loosened by the fluidizing plate 15. If the desired operating pressure is reached, the conveying of the pulverized fuel can begin by opening of the valve 11 and, by means of the quantity-measuring means 9, which activates the control valve 11, and optionally by means of additional gas 8 being supplied to the powder-conveying line 14, the desired amount of fuel can be set. The pulverized fuel is supplied via the powder-conveying line 14 to the gasifying reactor 7, in which the conversion with the gasifying means oxygen and optionally steam, but also carbon dioxide to form gasifying gas is undertaken. The gasifying gas is supplied to corresponding plants/devices for further treatment via the line 12. The powder-conveying lines 6 and 14 can have dimensions of between 10 and 100 mm. The distance between the combined powder-locking and metering vessel 5 and the gasifying reactor 7 is 200 m.

(7) During the desired supply of powder, a pressure loss between the vessel 5 and the entrained-flow gasifying reactor 7 of 0.7 MPa arises at an overall plant pressure of 4.7 MPa. This corresponds to approximately 15% of the overall pressure. This value can be up to 20%.

(8) In order to ensure continuous operation, before the complete emptying of the locking and metering vessel 5 which is in operation, the switch is made to a second locking and metering vessel 5 without the continuity of the powder flow in line 14 being disturbed. This takes place after the filling and tensioning operation of the second locking and metering vessel 5 is finished. The desired value for the mass flow control of the coal of 82 Mg/h is subsequently divided between the control valves 11 of the first and second locking and metering vessels 5, wherein the portion divider 18 conducts the desired value from the first valve to the second valve. The desired value here is displaced by a ramp, the time t1 of which can be set. The ramp exit is multiplied by the desired value of the mass flow for the second control valve 11 and, for the first control valve 11, the ramp exit is subtracted from 1 and multiplied by the desired value of the mass flow. In this manner, constant conveying into the gasifying reactor 7 during the readjustment to the other locking and metering vessel 5 can be ensured. A further influencing of the powder flow control, in particular also fine control, can be undertaken by the control valves 17 located in the fluidizing gas line 16 or by the supply of additional gas 8 into the auxiliary gas feed 13 of the powder-conveying line 14.

Example 2

(9) A gasifying plant according to FIG. 2, simplified and illustrated without 11, 17, 18, provides the same capacity as in Example 1. The distance between the combined powder-locking and metering vessels 5 and the entrained-flow gasifying reactor 7 is approx. 500 m. In order to limit the pressure loss in the powder-conveying lines 6 and 14 and also to keep the flow speed below 8.5 m/s, a powder flow divider 19 is inserted into the powder-conveying line 14 after a distance of 250 m, said powder flow divider dividing the powder flow uniformly between the three powder-conveying lines 14a, b, c. The three powder-conveying lines 14a, b, c can be connected to the three galvanized-fuel supply means of a high-power burner or in each case to the pulverized-fuel supply means of one of three burners. The further operation corresponds to Example 1.

(10) A quantity-measuring means and controller for the entire powder flow 21 can be arranged in the powder-conveying line 14 common to the powder-locking and metering vessels 5. In accordance with the mass flow determined in the quantity-measuring means and controller for the entire powder flow 21, the quantity of fluidizing gas flowing into the powder-locking and metering vessels 5 in total is controllable via a control valve for the entire amount of fluidizing gas 22 in the fluidizing gas line 16 with the effect of a master control means.

Example 3

(11) An entrained-flow gasifying plant with an output of likewise 500 MW is supplied with 82 Mg/h of pulverized fuel over a distance of 500 m, said pulverized fuel being placed under pressure in three combined powder-locking and metering vessels 5 and being fed into the powder-conveying lines 14. The diameters of the conveying lines are 0.06 m. In order to limit the pressure loss in the powder-conveying lines and the flow speed of the gas and pulverized fuel suspension the cross sections of said lines are doubled after a conveying distance of 250 m such that the diameters thereof are increased to 0.085 m.

(12) The invention is also provided by a system for the pneumatic feeding-in of pulverized fuel according to the continuous-conveying principle in an entrained-flow gasifying reactor 7, in particular overcoming conveying distances of 80 to 500 m, in which a H2- and CO-rich crude gas is produced by conversion of gasifying means with oxygen or containing free oxygen at pressures of between 1 and 10 MPa and temperatures between 1300 and 1600 C., wherein an untreated fuel stored in an untreated fuel silo 2 is supplied to a device 3 for drying and grinding the fuel to form powdery fuel, the pulverized fuel is subsequently freed from the entrained drying and circulating gas in the filter 4, in a combined powder-locking and metering vessel 5, the pulverized fuel is set under operating pressure and is introduced in the fluidized state and in a defined flow into a powder-conveying line 14, in the fluidized state, the pulverized fuel is supplied by means of continuous conveying through the powder-conveying line 14 to the entrained-flow gasifying reactor 7, there are a plurality of combined powder-locking and metering vessels 5 which are discontinuously (cyclically) filled with pulverized fuel and set under pressure and the content of which is supplied continuously to the entrained-flow gasifying reactor 7 by, after the filling and tensioning operation, the desired value for the mass-flow control of the pulverized fuel being divided between the control valves 11 of the powder-conveying lines 6 of the first and second powder-locking and metering vessels 5, wherein the desired value is displaced from the first control valve 11 to the second control valve 11 via a portion divider 18 and, in the process, the desired value is displaced via a ramp, the time t1 of which can be set, and the ramp exit is multiplied by the desired value of the mass flow for the second control valve 11 and, for the first control valve, the ramp exit is subtracted from 1 and multiplied by the desired value of the mass flow, wherein, in parallel to the activation of the control valves 11, the supply of fluidizing gas 16 under the fluidizing plates 15 is started and the conveying begun.