JPS6267240A - Fuel converting method for burner - Google Patents

Abstract

PURPOSE:To reduce load variation, by separating burners in a multistage combustion type burner into plural groups, and operating a burner transfer between stages in a group followed by that of the other groups. CONSTITUTION:The whole flow 80 of primary burners 7 is separated into flows 21 and 31, while the whole flow 90 of secondary burners 8 is separated into flows 22 and 32. When the burning is transferred from the primary burners 7 to the secondary burners 8, the flow 31 of group B of the flows 31 and 32 is reduced in the mode 1, while the flow 22 of group A of the flows 21 and 22 is increased in the mode 2 in the same value as the reduction of the group B. In the same way, the flow 21 of the group A is reduced while the flow 32 of the group B is increased in the mode 3 in the same value. Therefore, the load variation in the fuel converting can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a combustor for a gas turbine, and in particular to a combustor for a gas turbine.
The present invention relates to a fuel switching method for each stage of a two-stage or multi-stage combustion method employed in an Ox combustor.

[Background of the invention]

In a low NOx combustor, fuel is dispersed and combusted in two or multiple stages in order to reduce the exhaust NOx concentration. Therefore, the number of burners is plural. Here, a two-stage combustion method will be explained as a conventional technique.

In this method, there is a first-stage burner and a second-stage burner, and only the first-stage burner operates when the rotation speed increases and the load is low at startup. Furthermore, when increasing the load, the first stage burner is moved and the second stage burner is also ignited.

This is called fuel switching.

In this case, in order to avoid load fluctuations in the gas turbine, the fuel flow rate of the first-stage burner is throttled, and that amount of fuel is supplied to the second-stage burner to keep the total amount of fuel constant.

Therefore, the fire must be transferred to the second stage burner.

At that time, there is a mutually contradictory requirement that the spark of the first stage burner must be made small.

A low NOx combustor, no matter how good its other performances are, will not have a chance to take advantage of its features unless the fuel is reliably switched from the first stage burner to the second stage burner. Therefore, fuel switching requires 10(l reliability).

The present invention satisfies the above-mentioned seemingly contradictory requirements.

[Purpose of the invention]

An object of the present invention is to eliminate gas turbine load fluctuations when transferring fire from the first stage burner to the second stage burner.

Another object of the present invention is to provide a 100% reliable fuel switching method.

[Summary of the Invention] The main point of the present invention is that in a multi-can combustor, for example, if the total number of combustors is ten, it is divided into Nigel loops, the fuel of one group is switched first, and it takes some time. The purpose is to delay the fuel switching for the other group.

[Embodiments of the invention]

In FIG. 1, 100 indicates the total fuel flow rate of the gas-fired gas turbine. 80 indicates the total fuel flow rate of the first stage burner 7. 90 indicates the total fuel flow rate of the two-stage burner 8. 80 is
Divided into flow rates 21 and 31, the former is group A and the latter is group B.
It's called a group. 9° is divided into flow rates 22 and 32, the former being called the A group (5 cans) and the latter the B group (5 cans).

These lines 21, 22, 31.32 have pressure regulating valves 41, 42, 51.52, respectively, which regulate the pressure in front of the flow regulating valves 61, 62, 71.72. flow control valve 6
1, 62, 71, and 72 adjust the fuel flow rate according to the load of the gas turbine.

11 to 20 indicate gas turbine combustors (IT 10 cans), and as a representative example, 111 indicates the fuel supply piping of the first stage burner.
．． The fuel # and amount piping to the two-stage burner is shown at 112.

FIG. 2 shows the fire transfer (fuel switching) schedule from the first-stage burner to the second-stage burner, which is the essence of the present invention.

In this way, the fuel flow rate 80 is the sum of 21 and 31, and in mode 1, the A group first stage burner fuel flow 121 is kept constant, the B group first stage burner fuel flow rate 31 is gradually decreased, and the A group Increase the second burner fuel flow rate 22.

A group's fire changed at 5 of the ascending process of 22 (fuel switching)
will be carried out reliably.

In mode 2, the A group first stage burner fuel flow cover 21 is gradually decreased, and the B group first stage burner fuel flow 3131 is gradually increased and returned by that amount, and the large group second stage burner fuel flow rate 22Vi is kept constant. Once Osugi-shi has been completed to 22, the fire will not be extinguished even if the number is reduced to 21.

In mode 3, B group first stage burner fuel fi13
1 is kept constant, the A group first stage burner fuel flow rate 21 is further decreased, and the B group second stage burner fuel flow rate 32 is gradually increased by that amount. At step 6 of the ascending process of step 32, the fire transfer (fuel switching) of group B is reliably performed.

In mode 4, the B group first-stage burner fuel flow rate 31 is gradually decreased, and at the same time, the second-stage burner fuel flow rate 22.32 is gradually increased to bring the fuel flow rates of the first-stage and second-stage burners to predetermined values. Fuel switching is completed in the above four modes.

〔Effect of the invention〕

According to the present invention, it is possible to eliminate load fluctuations in the gas turbine during fuel switching in a low NOx combustor, and to reliably transfer fire from the first-stage burner to the second-stage burner in terms of loO.

[Brief explanation of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention, and FIG. 2 is a diagram showing a fire transfer (fuel switching) schedule from the first-stage burner to the second-stage burner of the present invention. 21...First stage flow rate of group A, 22...
The flow rate of the two-stage burner of the A group, 31.32...The flow rate of the B group, respectively, 80...The sum of the flow rates of the first stage of 21 and 31, 90...The second stage of 22 and 32. (−
shows the sum of the flow rates.

Claims (1)

[Claims] 1. In a combustor using a multi-stage combustion method, the combustor is divided into a plurality of groups, one group's inter-stage flame transfer is performed, and the other groups are then chronologically transferred between the stages. A combustor fuel switching method characterized by performing a fuel transfer.