JPH0249915A - Method for purifying exhaust gas from stationary diesel engine - Google Patents

Abstract

PURPOSE:To reduce the exhausted amount of NOx and soot contained in the exhaust gas from a Diesel engine by using the gas as part of the air for combustion in a combustor such as boiler, and by combusting hydrocarbon fuel. CONSTITUTION:Exhaust gas from a Diesel engine 1 is passed through an exhaust gas duct line 2, introduced into the air for secondary combustion of the fuel in a burner 5 of a boiler 3, and used as the air for combustion of the fuel. Reduction of NOx in the exhaust gas by the fuel (hydrocarbons) shall take place at a combustion reaction band in the boiler 3 and its backstream. The air ratio in the combustion reaction band shall be in the condition to allow imperfect combustion of the fuel under reductive atmosphere, and the uncombusted portion or unreacted gas in this region are combusted perfectly by adding air for two-stage combustion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an effective and economical method for purifying high 1 degree NO and soot discharged from a stationary diesel engine, and a method for blowing diesel exhaust gas therein.

N08 emitted from stationary diesel engines is approximately 80
The amount of nitrogen oxides is 0 to 1,300 ppm, and compared to soot-producing facilities such as boilers, the amount of nitrogen oxides emitted per unit of fuel used is extremely large. In the past, diesel exhaust gas was released into the atmosphere untreated as it was not subject to the Air Pollution Control Act, but now it is now subject to regulations and must be purified before being released into the atmosphere due to the need for air conservation. Although methods for suppressing N08 in diesel engines have already been considered, the after-treatment of diesel exhaust gas has not yet been studied much. Denitrification methods for soot and smoke generating facilities such as boilers have been established, so it is possible to use such denitrification equipment, but since diesel exhaust gas contains soot in addition to NOx, conventional denitrification equipment is not suitable. It is difficult to imagine that it can necessarily be applied as is.

This method assumes that a combustion device such as a boiler is installed or can be installed near the diesel engine. Diesel exhaust gas contains a large amount of residual oxygen (approximately 13%), and this diesel exhaust gas is used as part of the combustion air for combustion equipment such as boilers.
It burns hydrocarbon fuel and at the same time reduces the high concentration of NOx and soot in diesel exhaust gas.

A conceptual diagram on which the present invention is based is shown in FIG.

FIG. 1 shows a plant that combines diesel exhaust gas and a combustor such as a boiler, where 1 is a diesel engine, 2 is a duct line for diesel exhaust gas, and 3 is a boiler. 4 is a burner-like box, and 5 is a burner. Exhaust gas discharged from the diesel engine 1 is introduced into the burner 5 of the boiler 3 through the exhaust gas duct line 2, and is introduced into the air for secondary combustion of fuel and used as air for combustion of the fuel. In this case, the diesel exhaust gas must be introduced upstream of the combustion reaction zone because the fuel needs to be combusted in a reducing atmosphere. That is, NO in diesel exhaust gas
The reduction using the fuel (hydrocarbon) of No. 8 is carried out in the combustion reaction zone and on the downstream side thereof. As long as the diesel exhaust gas temperature is 180°C or higher at the boiler introduction part, it can be used as is. Note that it is preferable to introduce the exhaust gas into the secondary combustion air of the burner, but if this is not possible, the exhaust gas may be blown into the combustion reaction zone in parallel with the burner axis. The stability of the burner flame due to diesel exhaust gas injection is good because it uses not only diesel exhaust gas as combustion air but also air□.

As shown in Figure 2, the air ratio in the combustion reaction zone must be such that the fuel is incompletely combusted in a reducing atmosphere. Complete combustion is achieved by adding

Further, soot in diesel exhaust gas, as well as soot generated when burning fuel, can be almost completely removed by two-stage combustion at an air ratio of 1.1 or more and a temperature of 900°C or more.

FIG. 2 shows an example of the results of an experiment for purifying diesel exhaust gas by mixing diesel exhaust gas into secondary air for combustion using a test furnace having one burner. The initial concentration of N08 in diesel exhaust gas is 1520 ppm. The air ratio is the ratio between the actual amount of air used for combustion and the theoretical amount of air, where W is the mass concentration, F is the fuel, 0 is the oxidizer,
When exp is the setting condition and 5toich is the stoichiometric condition, 1 (WF/WCI).

λ (“IVF/Wo) st. 1°.

Defined as

Here, the secondary air ratio means the air ratio during burner combustion alone, and the total air ratio represents the total air ratio taking into account the primary air ratio, the air for second stage combustion, etc. In the case of this experiment, when the primary air ratio is 0.84, the minimum NO, il is 1 degree, and when the total air ratio is 11 to 1.3, NOx is 160 = 1
80 ppm+, and the NOx removal rate is 88 to 89%, which can be suppressed very well.

Figure 3 shows an example of the results of an experiment in which diesel exhaust gas was blown into the flame zone. In this case, the NoX #tj rate is higher when the air ratio is low, but even though there is a difference in the blowing method, when the primary air ratio is in a reducing atmosphere, NOx in diesel exhaust gas is very low. Can be returned,
In particular, a higher N08 suppression rate can be obtained when diesel exhaust gas is blown in together with the burner's secondary combustion air.

The above is based on the principle of NOx suppression, NO8 suppression technology using hydrocarbons, and NOx suppression technology using exhaust gas recirculation.
This is a diesel exhaust gas control method that makes full use of a wide range of NO8 suppression technologies, including N08 suppression technology using two-stage combustion.

In this way, if hydrocarbon fuel is burned using day cell exhaust gas as part of the combustion air of a combustion device such as a boiler, high concentrations of NO8 and soot can be effectively suppressed, and other denitrification equipment can be added. This is an economical method as there is nothing to do.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the concept underlying the present invention.
This shows a plant that introduces stationary day cell engine exhaust gas into a boiler and burns it. FIGS. 2 and 3 are graphs of examples in which diesel is purified by the blowing method. l... Diesel engine 2... Diesel exhaust gas duct line 3... Boiler 4... Burner melon box 5... Burner 2nd diagram

Claims (3)

[Claims] (1) From a stationary diesel exhaust gas engine characterized by reducing NO_x and soot in diesel exhaust gas by using diesel exhaust gas as part of the combustion air of a combustor such as a boiler and burning hydrocarbon fuel. How to purify exhaust gas (2) A method for purifying exhaust gas from a stationary diesel engine, characterized by blowing diesel exhaust gas as part of the combustion air and as secondary air of a burner in a boiler, etc. (3) A method for purifying exhaust gas from a stationary diesel engine, characterized by blowing diesel exhaust gas as part of combustion air into a combustion reaction zone in parallel with the burner shaft of a boiler or the like.