JPH0517303U - Waste heat recovery boiler for diesel engine - Google Patents

Abstract

(57) [Summary] [Purpose] It is possible to reduce NOx in exhaust gas from diesel engines. [Structure] In a waste heat recovery boiler for recovering heat of exhaust gas from a diesel engine 2, the waste heat recovery boiler 1 includes:
A secondary combustion air supply means 4 for supplying additional combustion fuel, a primary combustion air supply means 7 for supplying the exhaust gas as primary combustion air, and a secondary combustion air supply means for supplying secondary combustion air downstream thereof are provided. The feature is that 8 is provided.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a waste heat recovery boiler for a diesel engine, which recovers heat of exhaust gas from the diesel engine.

[0002]

[Prior Art]

 Exhaust gas emitted from a diesel engine (for example, a diesel engine for power generation) has a high temperature (for example, 300 to 400 ° C), so the preheat of this exhaust gas is recovered as steam by a waste heat recovery boiler.

In the waste heat recovery boiler, the amount of heat of the exhaust gas alone is relatively small as necessary, and therefore the amount of heat is increased by burning the additional fuel such as heavy oil.

[0004]

[Problems to be solved by the device]

 By the way, the exhaust gas from the diesel engine contains 500 to 1500 ppm of nitrogen oxides (hereinafter referred to as “NOx”), and even if the diesel engine and the waste heat recovery boiler are combined, The gas emitted from the heat recovery boiler contains the NOx thereof with almost no reduction. For this reason, the denitration device provided downstream of the waste heat recovery boiler becomes large in size, which poses a problem in terms of equipment and cost.

Therefore, the present invention has been made in view of such circumstances, and an object thereof is to recover waste heat of a diesel engine that enables reduction of NOx in exhaust gas from a diesel engine. To provide a boiler.

[0006]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the present invention provides a waste heat recovery boiler that recovers heat of exhaust gas from a diesel engine, and is provided with a supplementary fuel supply means for supplying a supplementary fuel to the waste heat recovery boiler. A primary combustion air supply means for supplying the exhaust gas as primary combustion air is provided, and a secondary combustion air supply means for supplying the secondary combustion air is provided downstream thereof.

[0007]

[Action]

 The refueling fuel supplied into the waste heat recovery boiler is primarily combusted by the primary combustion air whose air ratio to this fuel is 1 or less, and is completely combusted downstream by the secondary combustion air which is insufficient to a predetermined air ratio. To be done. The primary combustion with a low oxygen concentration produces a NOx reducing substance, and the NOx reducing substance reduces NOx in the exhaust gas supplied as the primary combustion air. Therefore, NOx in the exhaust gas can be reduced by the waste heat recovery boiler.

[0008]

【Example】

 An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a waste heat recovery boiler that recovers heat of exhaust gas (O ₂ : 11 to 13%, 300 to 400 ° C., NOx: 500 to 1500 ppm) from a diesel engine, for example, a diesel engine 2 for power generation. Is shown, and a gas line 3 for discharging the gas in the boiler 1 is connected to the upper part thereof.

At the lower part of the waste heat recovery boiler 1, an additional heating burner 4 which is an additional heating fuel supply means for ejecting additional heating fuel such as heavy oil and primary combustion air into the boiler 1 and burning the fuel is provided. It is distributed. An exhaust gas line 6 for introducing the exhaust gas from the diesel engine 2 for power generation is connected to the wind box 5 of the additional combustion burner 4 to form a primary combustion air supply means 7, and the gas from the exhaust gas line 6 is connected. The air ratio to the reburning fuel is suppressed to 1 or less (for example, 0.7) through the wind box 5 and is ejected from the reburning burner 4 into the boiler 1 as primary combustion air.

Further, downstream or above the reburning burner 4, a secondary combustion air which is a constituent element of a secondary combustion air supply means 8 for supplying a shortage of secondary combustion air to a predetermined air ratio. A port 9 is provided, and a secondary combustion air line 10 connected to the exhaust gas line 6 is connected to the port 9.

An air supply line 12 having an air fan 11 is connected to the secondary combustion air line 10, and a branch line 13 branched from the air supply line 12 is connected to the exhaust gas line 6. The exhaust gas line 6, the secondary combustion air line 10, the air supply line 12 and the branch line 13 are provided with first, second, third and fourth on-off valves 14, 15, 16, 17 respectively. Therefore, the openings of the on-off valves 14, 15, 16, 17 are controlled so that the exhaust gas from the diesel engine 2 for power generation is supplied to the boiler 1 as primary combustion air as much as possible. It is being touched. For example, when the exhaust gas from the diesel engine 2 for power generation can cover the primary and secondary combustion air, the first and second opening / closing valves 14 and 15 are opened, and the third and fourth opening / closing valves 16 and 17 are closed. Become. When all the exhaust gas from the diesel engine 2 for power generation can be supplied to the boiler 1 as the primary combustion air, the first and third opening / closing valves 14 and 16 are opened and the second opening / closing valve 15 is closed. The opening degree of the fourth opening / closing valve 17 is adjusted as necessary. That is, in the exhaust gas from the diesel engine 2 for power generation, oxygen is 11 to 13%, which is considerably low in combustion, so that air should be supplied to the secondary combustion air port 9 and the wind box 5 as necessary. Is becoming

Next, the operation of this embodiment will be described.

The gas supplied from the exhaust gas line 6 to the wind box 5 is suppressed to have an air ratio with respect to the reburning fuel of 1 or less (for example, 0.7), and is burned from the reburning burner 4 into the boiler 1 as primary combustion air to be fuel oil. It is ejected together with the additional fuel such as, and the fuel is primarily burned. Due to this lack of air combustion, unburned components are generated, and the unburned components are completely removed by the insufficient secondary combustion air to a predetermined air ratio from the secondary combustion air port 9 provided above the burner 4. The exhaust gas is burned and flows into the gas line 3.

When the fuel is primarily burned with an oxygen amount smaller than the amount of oxygen required for burning the fuel, NOx reducing substances such as cyan and amine are produced, and the NOx reducing substances suppress the generation of NOx due to combustion. At the same time, the produced NOx is reduced (decomposed) to become harmless N ₂ . Therefore, if exhaust gas is supplied as primary combustion air, NOx contained in the gas will be reduced by the NOx reducing substance, and NOx contained in the exhaust gas will be reduced. This NOx reduction rate is about 50-60%. Is obtained. In this case, since the exhaust gas is supplied as the primary combustion air, NOx in the exhaust gas is reduced, and even if the exhaust gas is supplied as the secondary combustion air, the NOx in this gas is mostly converted by the unreacted reducing substance. Since it is not reduced, the first, second, third and fourth on-off valves 14, 15, 16, 17 are controlled so that the exhaust gas is supplied to the boiler 1 as primary combustion air as much as possible.

As a result, the exhaust gas from the diesel engine 2 for power generation is supplied to the waste heat recovery boiler 1 as primary combustion air, and NOx in the gas is converted to NOx by the NOx reducing substance generated by primary combustion with a low oxygen concentration. Since NOx is also reduced, NOx in exhaust gas can be reduced in the waste heat recovery boiler 1. As a result, the NOx concentration in the gas flowing into the gas line 3 will be lower than in the past, so that the denitration device provided downstream of the waste heat recovery boiler 1 can be downsized, and the equipment can be reduced in size and low. Cost can be reduced. Further, since oxygen contained in the exhaust gas in an amount of about 11 to 13% contributes to the combustion of the fuel, the oxygen in the exhaust gas can also be effectively used.

[0017]

[Effect of the device]

 In short, according to the present invention, the waste heat recovery boiler is provided with the additional combustion fuel supply means, the primary combustion air supply means for supplying the exhaust gas from the diesel engine as the primary combustion air, and the secondary combustion air supply means. It has an excellent effect of reducing NOx in exhaust gas from a diesel engine.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

[Explanation of symbols]

 1 Waste Heat Recovery Boiler 2 Diesel Engine (Diesel Engine for Power Generation) 4 Additional Burning Fuel Supply Means (Additional Burner) 7 Primary Combustion Air Supply Means 8 Secondary Combustion Air Supply Means

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shuzo Watanabe 3-2-16 Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industries Co., Ltd. Toyosu General Office (72) Inventor Masaaki Sasaki 3-5 Awajicho, Chuo-ku, Osaka No. 13 Omi Business Engineering Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. A waste heat recovery boiler for recovering heat of exhaust gas from a diesel engine, wherein the waste heat recovery boiler is provided with a reheating fuel supply means for supplying reheating fuel, and the exhaust gas is used as primary combustion air. A waste heat recovery boiler for a diesel engine, comprising primary combustion air supply means for supplying and secondary combustion air supply means for supplying secondary combustion air downstream thereof.