DD285989B5 - Procedure for commissioning gasification reactors - Google Patents

Description

For this 1 page drawing

Field of application of the invention

The invention relates to the process for fixed-bed pressure gasification of solid fossil fuels and in particular to the commissioning of fixed bed pressure gasification reactors, wherein the commissioning refers both to the ignition from the cold state as well as the start up under fire fixed bed pressure gasification reactors.

Characteristic of the known state of the art

The firing of fixed bed pressure gasification reactors for the gasification of coal is currently carried out according to two basic technical solutions.

Once a pilot fuel is fed to the reactor and either ignited before being fed or ignited by a Zündinitial in the reactor.

Thereafter, Anfahrluft is injected into the reactor, later gasification added and converted to an air-steam mixture.

The Anfahrrohgas is passed through a torch in the atmosphere until the volume fraction of oxygen is 0.6%.

In another solution, the reactor is filled with gasification material or partially filled, then heated by steam to above the autoignition temperature of the gasification material and finally ignited with an air-vapor mixture.

The assessment of the completed ignition is made by determining the Gv and CGy content in the starting raw gas. When set limit values are reached, the amount of air-steam mixture increases.

For safety reasons, the Anfahrrohgas is derived up to a volume fraction of oxygen of 0.6% via a flare system.

According to both technical solutions, when the following limits are reached:

Volume fraction of oxygen <0.6%

Volume fraction of CO ₂ in the raw gas> 23%

Raw gas outlet temperature> 200 ⁰ C and

Reactor pressure <0.6 MPa

switched from torch operation to a raw gas starting system. In this system, the starting raw gas is compressed to the usual network pressure and fed to the raw gas network.

The disadvantages of these technical solutions are high pollution of the environment during the torch operation lasting several hours, the energy required for compressing the Anfahrrohgases and that from the start of commissioning to the power circuit of the reactor, the resulting gas condensates must be dissipated in a specially required druckloscs gas condensate system ,

Due to the not fully closed design of the pressureless condensate system, the introduction of the hot gas condensates is also associated with a significant pollutant emission. The starting process under fire-stopped generators differs from the ignition process only in that the steps to the ignition of the gasification omitted. After the supply of the air-steam mixture, the process steps, such as Fährweise on the torch, driving on the Rohgasanfahrleitung and power circuit, made analogous to the technology described in the ignition process. The described disadvantages accordingly also occur.

It has also been proposed to use a steam-oxygen mixture in the commissioning of the reactors instead of a vapor-air mixture. As advantages, the shortening of the starting process, lower equipment costs and omission of the changeover from sinem steam-air mixture to a vapor-oxygen mixture and thus an expected safety advantage are given. However, the above-mentioned disadvantages can not be eliminated.

Also, some patents deal with the problem of commissioning of gasification reactors.

According to DE 3709 225 it is proposed to string the reactor in the starting process with superheated steam to the gasification pressure. The use of CO; in Anfahrvergasungsmittelgemisch is also described.

According to DD 200892, in the commissioning process of gasification reactors, a check of the oxygen content in the raw gas must be carried out and a limit value of less than 1% by volume must be observed.

Aim of the invention

The aim of the invention is to make the commissioning or recommissioning of coal-pressure gasification reactors more economical and environmentally friendly.

Explanation of the essence of the invention

The object of the invention is to make the start-up or restart of coal-pressure gasification reactors free of emission queues, especially of pollutant emission sources and to exclude the commissioning of the torch and the Rohgasanfahrtaitung and the non-pressurized gas condensate.

According to the invention, the object is achieved in that for the startup both for the ignition and for starting of under fire coal pressure gasification reactors, the supplied ignition-start gas mixture is varied in composition during the commissioning process, at the beginning of the commissioning process, the composition of the Zünd Start-Vergasungsmittelgemisches is designed so that the oxygen content is just so high that a steady increase in the temperature level in the reactor is possible, but on the other hand, an explosive gas mixture, even if not reacting the oxygen content in the reactor, can not arise. The ignition-start gasification mixture is adjusted in subcritical composition, which is to be understood as a critical composition of the O ₂ content in the inert gas, which would just be sufficient if not reacted in the reactor to form a explosive gas mixture in Anfahrrohgas or in the mixture Anfahrrohgas and raw gas , To accomplish this, inert gas components are used for the ignition-on-gasification mixture mixture which have a condensation temperature at given process pressures of less than 273K. Additional steam as a heat transfer medium can be used.

When using N ₂ or CO ₂ as the inert gas component, the volume fraction of oxygen should not exceed 5% in the first 30 minutes of commissioning and should not fall below 2.5%.

The pressure increase in the reactor takes place during ignition in the heating phase with steam by all the blowpipes are closed and inbetiiebnahme under fire standing reactors in the first minutes of'iibetriebnahmo by the natural pressure increase due to the initiation of the ignition-start gasification mixture. With the help of a continuously working OyAnalysenmessung a review of the G ₂ content in the raw gas is made. After 30 min pending volume fractions of the oxygen in the crude gas of less than 1%, the OyAnteil in the dry ignition-start gasification mixture is increased to 9% by the addition of oxygen. If the volume fraction of the oxygen after 30 min <1% in the raw gas, is converted to a gasification agent, which consists only of steam and oxygen.

Thereafter, at intervals of 15 minutes, a load increase of 100m ³ i. N. Oj / h up to an oxygen load of 1600m ³ i. N. O ₂ / h while maintaining a given, the coal properties corresponding vapor-to-oxygen ratio. Under this load, stabilization of the ash bed takes place for 4 hours. Thereafter, the desired load is adjusted stepwise.

During start-up operations of reactors under fire eliminates the stabilization phase of the ash bed. This method has the following advantages:

- The ignition and starting processes are emission-free.

- By a subcritical composition of Anfahrvergasungsmittels in the initial phase, a safe technique is realized.

- The gas discharge via the torch and the raw gas supply line is no longer made. This avoids gas losses and gas compression costs.

- The gas condensate discharge takes place when using the gas condensate pressure system trouble-free and without the pollutant emissions that occur in the slop system.

- The Vergasungsstoffaufheizung in a closed pressure system is better utilization of the enthalpy of steam and a safe ignition than in pressureless heating. The vapor emission to the atmosphere during the heating process is eliminated.

The invention will be explained in more detail below by means of two examples, wherein Example 1 represents an ignition process and Example 2 represents a starting process.

The applicable to both examples Figure 1 shows a process scheme.

example 1

The ignition process is characterized by the following successive process steps:

1. Full locks the reactor 4 with coal

2. inerting of the coal-filled reactor 4, including the scrubber 5, waste heat boiler 6 and raw gas eitung 7 existing Rohgasweges up to the Inertisierungsstutzen 8 in front of the closed gate valve 9 in the crude gas with inert gas, consisting of N ₂ or CO ₂ , via the corresponding nitrogen or CO _{2 line} 1 is introduced, via the injector 2 and the Vergasungsmittelgemischleitung 3.

3. Tension of the filled with coal gasification reactor with steam over du motive steam pipe 10 with a steam amount of 5t / h up to operating pressure. All pipes discharging from the raw gas system are closed.

4. Mains circuit of the reactor 4 upon reaching the network pressure in the reactor.

5. preheating the coal in the reactor 4 with a gasification vapor of 15t via the motive steam line 10, the injector 2 and the Vergasungsmittelgemischleitung 3rd

6. Ignition of the gasification material after a heating time of one hour at a steam temperature after the reactor of about 523K means of 3ine ignition-start gasification mixture with subcritical composition of 2000m ³ i. N.N ₂ / h and a volume fraction of oxygen of 4% via the N ₂ line 1 and the Mengenrägelung 12. The steam supply is suspended.

7. Gas mixture mixture adjustment according to the following program:

The volume fraction of oxygen in the ignition-start gas mixture is increased by 5% when the volume fraction of the oxygen in the starting raw gas is less than 1% for 30 minutes.

Remains at a volume fraction of the oxygen of 9% in the ignition-start gasification agent for 30 minutes, the volume fraction of oxygen in Anfahrrohgas below 1%, is on a pure steam-oxygen mixture line 10 and 11 of 200m ³ i. N. O ₂ / h and 1.5t steam / h converted.

8. The adjustment of the reactor load or the normal operation is carried out when in the latter setting according to point 7 in a period of 30 min, the volume fraction of the oxygen in the starting raw gas below 0.6% and the raw gas outlet temperature is 503K. The increase in the O ₂ amount is carried out in increments of 15 min by 100 m ¹ i. N. O ₂ / h while maintaining a steam-oxygen ratio of 7.5 kg steam / m ³ i. N. O ₁ , wherein the height of the steam-oxygen ratio is adapted to the ash melting behavior.

Example 2

The difference to the ignition process results from the differing starting conditions in the reactor. If, at the beginning of an ignition process, the reactor is still completely empty, an ignited gasification substance is already present in the reactor when a starting process is initiated. Such conditions usually arise when generators for the purpose of doing certain repairs must be taken out of service.

The individual process steps for a startup process are:

1. inerting of the reactor via the inerting line 13 at the reactor head up to the inertizing nozzle 8 before the closed separating slide 9 in the crude gas line by means of inert gas. The volume fraction of the oxygen in the crude gas line must be less than 4%.

2. Initiation of a start-up gasification mixture via the line 1 with subcritical composition of 2COOm ³ iN / h and a volume fraction of oxygen of 4% by means of flow control 12 in the reactor 4. In this case, all lines leading from the raw gas system are closed.

3. Mains circuit of the reactor upon reaching the network pressure in the reactor. The volume fraction of the oxygen in the starting raw gas must be less than 5%.

4. The further process steps are analogous to the points 7 and 8 of the ignition process.

List of reference numbers used

1 nitrogen or CGv line

2 injectors

3 gasification mixture line

4 reactor

5 washing coolers

6 waste heat boiler

7 raw gas line

8 inertizing nozzles

9 isolating slide

10 motive steam line

11 oxygen line

12 Volume control

13 inerting line at the reactor head

Claims (4)

1. A method for commissioning of gasification reactors of the fixed bed pressure gasification, suitable both for the ignition, as well as for startup of gasification under gasification reactors and covering the gasification reactors with inert media to network pressure, characterized in that said in the said commissioning processes a Volumenantail of oxygen in the dry starting-gasification mixture is set between 5% and 2.5%, which must not übar- or falls below, until 30 min long in Anfahrrohgas the volume fraction of oxygen is known to be less than 1%, with the standing at mains pressure Anfahrrohgas immediately is fed into the raw gas network, and that after this oxygen volume fraction has stood for 30 min, the oxygen volume fraction in the ignition-start gas mixture increased to 9% witd, and then after a further 30 min, the volume fraction of the oxygen in the raw gas is less than 1%, on a Vergasungsmittelgems ch switched, which consists only of steam and oxygen and that further after conversion to this steam-oxygen mixture and reaching a Rohgasaustrittstemperatur after the reactor of at least 503Kin intervals of 15 minutes, a load increase of 10Om ³ O ₂ iN / h to a Oxygen load of 1600m ³ iN / h takes place, whereby the maintenance of a predetermined vapor-oxygen ratio is necessary. 2. The method according to claim 1, characterized in that the heating of the gasification material for the ignition process is carried out with a gasification vapor amount of 10 to 20t, wherein the temperature at the crude gas outlet of the gasification reactor at the end of the heating must be at least 523 K. 3. The method according to claim 1, characterized in that are included in the ignition start-gas mixture inert gas components which have a condensation temperature at a given process pressure of less than 273 K. 4. The method according to claim 1 and 3, characterized in that the inert gas components are N ₂ or CO ₂ , wherein in addition steam can be used as a heat carrier.