AU2013270717A1

AU2013270717A1 - Method for operating a bulk material lock means

Info

Publication number: AU2013270717A1
Application number: AU2013270717A
Authority: AU
Inventors: Frederic Judas; Erhard Lath
Original assignee: Air Liquide SA; LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Current assignee: Nalwa Special Steel Raigarh Ltd
Priority date: 2012-06-05
Filing date: 2013-06-03
Publication date: 2014-08-14
Anticipated expiration: 2033-06-03
Also published as: IN2014DN06586A; WO2013182516A1; RU2584014C2; ZA201405074B; KR20150023221A; DE102012104866B4; CN104302742B; KR102085013B1; RU2014135168A; AU2013270717B2; DE102012104866A1; UA112464C2; CN104302742A

Abstract

A method for operating a system of bulk material locks which are used for filling tanks or reactors under positive pressure, wherein during depressurization of the locks the gas and the pressure energy in part are stored by pressure compensation with one or more pressure tanks and are reused during pressurization.

Description

WO 2013/182516 PCT/EP2013/061374 Method for Operating a Bulk Material Lock Means 5 Field of the Invention This invention relates to a method for operating a system of bulk material locks which are each used for filling a processing apparatus under positive pressure, which contains a process gas, such as a tank or reactor, wherein prior to filling with bulk material the locks are depressurized to atmospheric pressure and the 10 escaping gas is collected in one or more tanks and stored for further use, and wherein prior to draining their bulk material content into the tank or reactor the locks are pressurized to its operating pressure with process gas. Such system of bulk material locks is formed by the locks of a production plant comprising a plurality of substantially identical processing apparatuses. 15 Prior art Methods for operating bulk material locks, which serve for filling processing apparatuses under positive pressure, are known. A very well-known example for such method is the charging of blast furnaces in the steel industry. When depressurizing the lock, the gas is collected, dedusted and stored in a gasometer, 20 from which it is supplied to its use, in general as fuel gas. For again pressurizing the lock, process gas is withdrawn from the blast furnace directly or after dedusting. Here, it is not required to reuse the collected gas itself for pressurizing the lock, as the blast furnace process will produce a sufficient quantity of blast furnace gas, in order to be able to branch off the gas required for pressurizing the 25 bulk material lock without disturbing the blast-furnace process. Cf. Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, Vol. 18, Iron, Chap. 2.5. What is not so favorable is the situation in plants of coal gasifiers, as they are described in principle in Ullmann's Encyclopedia of Industrial Chemistry, Sixth WO 2013/182516 PCT/EP2013/061374 2 Edition, Vol. 15, Gas Production, Chap. 4.4. A typical example for this technology is described in the German laid-open publication DE 10 2007 017 402 Al. These coal gasifiers, also referred to as pressure gasifiers, are of the shaft-like type. In these gasifiers, solid fuels such as peat, lignite, hard coal, coke, biomass 5 or the like are converted into a combustible product gas whose essential components are carbon monoxide and hydrogen. The shaft-like pressure gasifier is charged with the fuel from above. In the shaft, the fuel forms a fixed bed which is countercurrently traversed by a gas mixture which substantially consists of oxygen, or air, and steam. The product gas, whose temperature usually is up to 10 800 OC, is withdrawn in the upper region of the pressure gasifier and supplied to a purification and subsequently the utilization. The ash obtained from the fuel is discharged from the pressure gasifier at the bottom, e.g. via a rotating grate. The pressure gasification process typically is carried out at pressures between 15 and 50 bar. This results in the necessity to fill the fuel into the shaft via a bulk material 15 lock. For handing over the bulk material, or the fuel, the lock is pressurized with product gas to the process pressure existing in the shaft of the pressure gasifier and depressurized to ambient pressure for taking up its new charge. Other than in the blast furnaces of the steel industry, the gas represents the process product in the pressure gasification. At least in larger plants consisting of 20 several gasifiers it therefore is worthwhile to collect the gas discharged from the locks during depressurization, to compress it again to the operating pressure of the gasification process by means of a compressor unit and feed it back into the gas product stream. To carry out the pressurization of the locks by means of this compressor unit, 25 however, is not possible for economic reasons, since the very large gas quantity each required at short notice would require too large and expensive compressors. For pressurizing the locks, gas must therefore be branched off from the gasification process, wherein it must be accepted that with each removal of gas WO 2013/182516 PCT/EP2013/061374 3 for pressurizing the lock the uniform course of the gasification process is disturbed. Therefore, it has been the object to provide a method for operating a system of bulk material locks which avoids the disadvantages of the prior art in that less 5 depressurizing gas is obtained, which after compression must be fed back into the production process, and in that less pressurizing gas must be branched off from the production process. Description of the Invention The object is solved by a method with the features of claim 1. 10 The idea underlying the invention consists in that the locks each are depressurized in partial steps by pressure compensation with a pressure tank, so that in the one or more pressure tanks not only the gas, but also a part of the pressure energy present in the gas is stored. The smaller the distance between the starting pressure of the lock and that of the 15 pressure tank before pressure compensation, and the smaller the pressure tank, the more pressure energy can be stored. How many locks can be combined to such a system consisting of several locks and the one or more pressure tanks primarily depends on the frequency and duration of the lock cycles and on the number and duration of the pressure 20 compensation steps. Lock cycle here is understood to be the depressurization of the lock to atmospheric pressure, filling the lock with solids, pressurizing the lock to the operating pressure of the reactor, and discharging the solids from the lock into the reactor. 25 The method according to the invention can be designed advantageously according to the dependent claims 2 to 5.

WO 2013/182516 PCT/EP2013/061374 4 An advantageous aspect of the invention consists in that the first depressurizing step of a lock, which is effected even before the steps to be carried out according to claim 1, is effected by pressure compensation with another lock of the system, which already has gone through the pressurizing steps c) and d) according to 5 claim 1. In this way, an even larger amount of gas and pressure energy is preserved and for the lock to be pressurized less gas must be withdrawn from the gasification process, in order to achieve the necessary operating pressure in the lock for handing over the solids into the reactor. A further preferred aspect of the invention consists in that the last step for 10 pressurizing the lock to the operating pressure of the connected apparatus is effected in that a pressure compensation is carried out between the lock and the apparatus. In many applications, this step is problematic, since the gas withdrawn directly from the apparatus can be very hot and can contain constituents which are deposited in the lock and can lead to malfunctions. In the present case, the 15 gas demand for this last pressurizing step is so low, however, that it can also be carried out at a high gas temperature and with a certain concentration of condensable constituents in the gas, without impairing the operability of the lock. A further preferred aspect of the invention consists in that after carrying out the depressurizing steps a) and b) according to claim 1 a further depressurizing step 20 takes place, in that a pressure compensation between the lock and a pressure tank, which serves as recipient tank for a compressor unit, is carried out, by means of which the gas is fed into the product stream of the plant supplied by the lock system. In this way, the process gas withdrawn from the process through the lock is recirculated and the yield of the process is increased. 25 A further advantageous aspect of the invention consists in that after carrying out the depressurization into the recipient tank of a compression unit a further depressurization, to almost ambient pressure, is carried out by pressure compensation with a gasometer. In this way, the maximum possible amount of WO 2013/182516 PCT/EP2013/061374 5 gas can be collected and stored. Due to the storage, the gas can be supplied to a further use, e.g. as fuel gas. As an alternative to the storage in a gasometer, it can however also be economic to dispose of the gas via a torch. 5 Particularly advantageously, the present invention can be used for carrying out methods for the pressure gasification of solid fuels. Since these methods are operated at pressures above the atmospheric pressure, the addition into the pressure gasifier must be effected via a lock, in order to disturb the gasification process as little as possible. While according to the prior art, the product gas 10 necessary for the pressurization of the locks exclusively is withdrawn from the pressure gasification process, the present invention in an economic way, i.e. without the installation of large compressors, provides for carrying out the pressurization of the locks in part with the gas drained from the locks during the depressurization. In this way, less gas must be withdrawn from the pressure 15 gasifier for pressurization and its process is disturbed less. The invention also comprises an apparatus for operating a method according to claims 1 to 5, comprising a system of bulk material locks, at least one of which each serves for filling a processing apparatus under positive pressure, wherein the system comprises at least one pressure tank and optionally a further pressure 20 tank with connected gas compression unit, a gasometer and a torch conduit, and wherein the locks, the tanks and the torch conduit are connected via pipe conduits such that every component can perform a gas exchange with every other component. Advantageously, the components are connected to a header conduit. In larger systems it can also be advantageous to use several header conduits, 25 e.g. one each for the pressure tank(s), the gas compression unit, the gasometer and/or the torch conduit. Exemplary Embodiments Further developments, advantages and possible applications of the invention can also be taken from the following description of exemplary embodiments and the WO 2013/182516 PCT/EP2013/061374 6 drawings. All features described and/or illustrated form the invention per se or in any combination, independent of their inclusion in the claims or their back reference. The drawing, Fig. 1, by way of example shows a partial view of a system of bulk 5 material locks according to the invention, equipped with two pressure tanks and a gasometer. The drawing, Fig. 2, by way of example shows a partial view of a system of bulk material locks according to the invention, equipped with two pressure tanks, a gasometer and a compressor unit, of which the gas recipient tank and the 10 compressor are shown. In the following example, the mode of function of the method according to the invention will be described with reference to two exemplary embodiments. Example 1 The bulk material supplied to the locks or discharged from the locks into a reactor 15 is indicated by the flow arrows or conduits 4, 5, 6 and 7. The bulk material locks A and B as well as the pressure tanks C and D each have a volume of 12.1 M 3 . The gasometer E serves for storing the depressurizing gas at almost atmospheric pressure. The blower F serves for conveying the gas via conduit 7 to its further use, e.g. as fuel gas, or to its disposal, e.g. via a torch. The locks, pressure tanks 20 and the gasometer are connected with each other for gas exchange via the conduits 8, 9, 10, 11, 12 and the header conduit 3. The conduits 1 and 2 serve the pressure compensation of the locks with the respective tank or reactor to be filled (not shown). Starting situation 25 - Lock A is filled with 54 vol-% of solids and with 46 vol-% of gas. It is at atmospheric pressure and is going be pressurized to the operating pressure of 50 bar(g) of the tank or reactor (not shown) supplied by the lock, in order to subsequently drain its solids content into the same.

WO 2013/182516 PCT/EP2013/061374 7 - Lock B has drained its solids content into the reactor (not shown) supplied by the same, is at the operating pressure of this reactor of 50 bar(g) and is going to be depressurized to atmospheric pressure, in order to again be filled with solids. 5 - Pressure tank C is at a pressure of 29.5 bar(g). - Pressure tank D is at a pressure of 38.8 bar(g). - Gasometer E constantly is at nominally atmospheric working pressure. Method step 1 - Pressure compensation between lock A and pressure tank C to 20.2 10 bar(g). Method step 2 - Pressure compensation between lock A and pressure tank D to 32.9 bar(g). Method step 3 15 - Pressure compensation between lock A and lock B to 44.6 bar(g). Method step 4 - Pressure compensation between lock A and the reactor to 50 bar(g). Method step 5 - Pressure compensation between lock B and pressure tank D to 38.8 20 bar(g). Method step 6 - Pressure compensation between lock B and pressure tank C to 29.5 bar(g).

WO 2013/182516 PCT/EP2013/061374 8 Method step 7 - Pressure compensation between lock B and the gasometer E to almost atmospheric pressure. Due to the procedure described in this example, 40 vol-% of the gas discharged 5 from the locks for depressurizing the same can be reused for pressurizing the locks. The remaining 60 vol-% of the depressurizing gas are discharged into the gasometer and disposed of from there via a torch and/or supplied to a use as fuel gas. In the prior art, 100 vol-% of the depressurizing gas must be treated in this way. A compression of this gas depressurized to atmospheric pressure to such an 10 extent that it might be used for pressurizing the locks, or that it might be admixed to the product gas at the outlet of the gasification reactors, is not economically expedient. Example 2 The bulk material supplied to the locks or discharged from the locks into a reactor 15 is indicated by the flow arrows or conduits 4', 5', 6' and 7'. The bulk material locks A' and B' as well as the pressure tanks C' and D' each have a volume of 12.1 M 3 . The gasometer E' serves for storing the depressurizing gas at almost atmospheric pressure. The blower F' serves for conveying the gas via conduit 7' to its further use, e.g. as fuel gas, or to its disposal, e.g. via a torch. The locks, pressure tanks 20 and the gasometer are connected with each other for gas exchange via the conduits 8', 9', 10', 11', 12' and the header conduit 3'. The conduits 1' and 2' serve the pressure compensation of the locks with the respective tank or reactor to be filled (not shown). In addition, the system comprises a compressor unit, represented by the gas 25 recipient tank G whose volume is 300 m 3 and the compressor H. The gas pressure in the gas recipient tank G is kept between 3 and 4 bar(g). The compressor H compresses the gas to the product gas pressure existing at the outlet of the gasification reactors (not shown). Via conduit 13, the tank G is filled WO 2013/182516 PCT/EP2013/061374 9 with depressurizing gas from the locks. Via conduit 14, the compressed gas is admixed to the product gas stream exiting from the gasification reactors. Starting situation - Lock A' is filled with 54 vol-% of solids and with 46 vol-% of gas. It is at 5 atmospheric pressure and is going be pressurized to the operating pressure of 50 bar(g) of the tank or reactor (not shown) supplied by the lock, in order to subsequently drain its solids content into the same. - Lock B' has drained its solids content into the reactor (not shown) supplied by the same, is at the operating pressure of this reactor of 50 bar(g) and is 10 going to be depressurized to atmospheric pressure, in order to again be filled with solids. - Pressure tank C' is at a pressure of 29.5 bar(g). - Pressure tank D' is at a pressure of 38.8 bar(g). - Gasometer E' constantly is at nominally atmospheric working pressure. 15 - Gas recipient tank G is at 3 bar(g). Method step 1 - Pressure compensation between lock A' and pressure tank C' to 20.2 bar(g). Method step 2 20 - Pressure compensation between lock A' and pressure tank D' to 32.9 bar(g). Method step 3 - Pressure compensation between lock A' and lock B' to 44.6 bar(g).

WO 2013/182516 PCT/EP2013/061374 10 Method step 4 - Pressure compensation between lock B' and the reactor to 50 bar(g). Method step 5 - Pressure compensation between lock B' and pressure tank D' to 38.8 5 bar(g). Method step 6 - Pressure compensation between lock B' and pressure tank C' to 29.5 bar(g). Method step 7 10 - Pressure compensation between lock B' and gas recipient tank G to 4 bar(g). Method step 8 - Pressure compensation between lock B' and the gasometer E' to almost atmospheric pressure. 15 Due to the procedure described in this example, 40 vol-% of the gas discharged from the locks for their depressurization can be reused for pressurizing the locks. Another 50 vol-% are compressed by means of the compression unit to such an extent that they can be admixed to the product gas stream of the gasification reactors. Only the remaining 10 vol-% must be discharged into the gasometer and 20 be disposed of from there or be supplied to the further subordinate use, e.g. as fuel gas.

WO 2013/182516 PCT/EP2013/061374 11 List of reference numerals A, B, A', B' bulk material lock 4, 5, 4', 5' addition of bulk material (conduits) 5 6, 7, 6', 7' discharge of bulk material to the reactor (conduits) 1,2,7,8,9,10,11,12,13, 1', 2', 7', 8', 9', 10', 11', 12', 13 pipe conduits for gas transfer 3, 3' header conduit C, D, C', D' pressure tank 10 E, E' gasometer F, F' blower G gas recipient tank H compressor bar(g) bar of positive pressure 15

Claims

1. A method for operating a system of bulk material locks which are each used for filling a processing apparatus containing a process gas under positive 5 pressure, such as a tank or reactor, wherein prior to filling with bulk material the locks are depressurized to atmospheric pressure and the escaping gas is collected in one or more tanks, such as pressure tanks or gasometers, and stored for further use, and wherein prior to draining their bulk material content into the apparatus the locks are pressurized to its operating pressure 10 with process gas, characterized in that depressurizing and pressurizing a lock comprises the following steps: a) a depressurizing step of the lock by pressure compensation with a pressure tank containing process gas, whose starting pressure lies below the starting pressure of the lock, 15 b) optionally one or more further depressurizing steps each by pressure compensation with one further pressure tank each containing process gas, wherein the initial pressure of the one or more further pressure tanks each lies below that of the pressure tank used in step a) or of the pressure tank used before, 20 c) optionally pressurizing steps by pressure compensation with the pressure tanks listed under b), starting with the tank at the lowest pressure and continuing with the respective tank at the next higher pressure, d) a pressurizing step by pressure compensation with the pressure tank 25 listed under step a).

2. The method according to claim 1, characterized in that before the pressurizing step a) of claim 1 a depressurizing step is effected by pressure compensation with another lock of the system, which first has been pre pressurized by the steps c) and d) according to claim 1. WO 2013/182516 PCT/EP2013/061374 13

3. The method according to any of the preceding claims, characterized in that the last pressurizing step for adjusting the lock pressure to the height of the operating pressure of the connected apparatus is effected by pressure compensation between the lock and the apparatus. 5

4. The method according to any of the preceding claims, characterized in that when depressurizing the lock, after carrying out the steps a) and b) of claim 1, a further depressurizing step is effected by pressure compensation of the lock with a pressure tank which serves as recipient tank for a compression unit. 10

5. The method according to any of the preceding claims, characterized in that when depressurizing the lock, after carrying out the steps a) and b) of claim 1, and after the depressurization in a pressure tank according to claim 4, the lock is depressurized by pressure compensation with a gasometer.

6. Use of a method according to any of the preceding claims for carrying out a 15 method for pressure gasification of solid fuels, characterized in that at least one bulk material lock each serves for filling a pressure gasifier of a shaft like type.

7. An apparatus for operating a method according to claims 1 to 5, comprising a system of bulk material locks, at least one of which each serves for filling a 20 processing apparatus under positive pressure, wherein the system comprises at least one pressure tank and optionally a further pressure tank with connected gas compression unit, a gasometer and a torch conduit, and wherein the locks, the tanks and the torch conduit are connected via pipe conduits such that every component can perform a gas exchange with every 25 other component.