JPH01288320A - Controlling method of ammonia denitrification device - Google Patents

Abstract

PURPOSE:To shorten a rise time by calculating the denitrification ratio by measuring the concentration of NOx in an exhaust gas in an intake and an outlet of an ammonia denitrification device and increasing the supply amount of ammonia based on the difference between the aimed denitrification ratio to the detected ratio. CONSTITUTION:As soon as an engine starts the operation and an exhaust gas begins to flow in a denitrification device, the concentration of NOx in the exhaust gas is detected by a detector 4 set in an intake of the denitrification device and the detected signal X3 is held in a holding element 7. Then, the NOx concentration is detected by a detector 5 in an outlet of the denitrification device. The detected concentration X4 and the held detected signal X3 are processed by a computing element 8 so as to calculate denitrification ratio (n). When an aimed denitrification ratio is assumed to be n0, the difference of the both n0-n=n is the amount of adsorbed ammonia. The necessary ammonia amount is thus calculated backward from (n) in the computing element 8 and a signal so as to increase the supply amount of ammonia in the (n) is fed forward to a controlling element 9.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a control method for an ammonia denitrification device that decomposes NOx components contained in exhaust gas from an internal combustion engine, etc. by reacting them with ammonia adsorbed on a catalyst. In particular, the present invention relates to a method for controlling the amount of ammonia supplied that can quickly increase the denitrification rate of an apparatus at the time of starting operation of an engine or the like.

[Prior Art] An ammonia denitrification device decomposes NOx components in exhaust gas generated by an internal combustion engine or the like by reacting them with ammonia adsorbed on a catalyst. Conventional ammonia supply control in such ammonia denitrification equipment involves measuring the NOx concentration in the population of the denitrification equipment, calculating this with the amount of exhaust gas, and supplying ammonia that matches the designed denitrification rate. Ta.

[Issues to be Solved by the Invention] In the ammonia denitrification apparatus as described above, the intended denitrification rate cannot be obtained unless the amount of ammonia adsorbed onto the catalyst matches the denitrification performance. - Numerically, such a denitrification device is used continuously, so that insufficient adsorption of ammonia occurs only, for example, during 3 to 4 hours after the start of operation of the engine. However, when using a diesel power generator for cogeneration that repeatedly starts and stops depending on the power demand, the above-mentioned ammonia adsorption is insufficient, and the time that it is operated at the planned denitrification rate is shortened. There was a problem that it became.

An object of the present invention is to increase the amount of ammonia supplied immediately after the start of operation of the engine in a control method for an ammonia denitrification device to hasten the adsorption of ammonia to the catalyst, thereby shortening the rise time of the denitrification rate compared to the conventional method. It is something to do.

[Means for Solving Problems] A control method for an ammonia denitrification device according to the present invention is a method for controlling an ammonia denitrification device in which No. 8 in exhaust gas discharged by an engine is reacted with ammonia adsorbed on a catalyst. At the start of operation, the NOx concentration in the exhaust gas at the inlet and outlet of the ammonia denitrification device is measured to calculate the denitrification rate, and the amount of ammonia supplied is increased based on the difference between the denitrification rate and the target denitrification rate. There is.

[Operation] After the engine starts operating, exhaust gas is sent to the ammonia denitrification device, and the actual NOx removal rate is calculated by measuring the NOx concentration in the exhaust gas at the inlet and outlet. If you calculate the amount of ammonia according to the difference between this denitrification rate and the target denitrification rate and increase the amount of ammonia supplied to the denitrification equipment by that amount,
The target denitrification rate can be reached in a short time.

[Example] An example of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 is a block diagram of a control device 1 of this embodiment that controls an ammonia denitration device (hereinafter referred to as a denitration device), which is not shown. This control device 1 receives detection signals Xi from a flow rate detector 2 that detects the amount of exhaust gas flowing from an engine (not shown) to a denitrification device (not shown) and an ammonia gas flow rate detector 3.

X2 is input, and the detector 4.5, which is installed at the inlet and outlet of the denitrification equipment and detects the NOx concentration in the exhaust gas, outputs No, concentration detection signals X, , X4.
is now being done manually. The control device 1 calculates the optimal ammonia gas flow rate from these various detection signals x1 to X4, and drives the flow rate control valve 6 to optimally adjust the amount of ammonia gas supplied to the denitrification device. It is.

First, when the engine starts operating and exhaust gas begins to flow into the denitrification device, the detector 4 at the inlet of the denitrification device detects the NoXfi degree in the exhaust gas flowing into the denitrification device, and sends the detection signal x3 to the holding element 7. Hold. Next, the NOx concentration in the exhaust gas flowing out from the denitrification device is detected by the detector 5 at the outlet of the denitrification device. This detection signal x4 and the held detection signal x3 are processed by the calculation element 8 to calculate the actual denitrification rate η of the denitrification device. If the target denitrification rate of the denitrification equipment is the design denitrification rate η0, the beam will rise immediately after the start of denitrification. 〉η, and the difference between the two is η. −η=Δη
becomes adsorbed ammonia. Therefore, calculation element 8
The necessary amount of ammonia may be calculated backward from Δη, and the signal may be fed forward to the controller 9 so as to increase the amount of ammonia supplied by Δη.

By the way, at this time, the detection signal x1 from the exhaust gas flow rate detector 2 is manually input to the ratio setter 11 via the linearizer 10. That is, the detection signal x1 is multiplied by a certain ratio set in the ratio setter 11, and the resultant signal is applied to the controller 9. On the other hand, the detection signal X2 output from the flow rate detector 3 of the ammonia gas to be controlled is input to the controller 9 after being processed by an appropriate transfer function, so it is input from the ratio setting device 11 to the controller 9. The signal x1 to be
Together with the feedforward signal from the calculation element 8, this becomes an ammonia gas flow rate setting signal. As a result, the valve 6 is operated by the control signal output from the controller 9, and the flow rate of the ammonia gas is adjusted to the above Δη at a constant ratio to the flow rate of the exhaust gas.
so that it increases by the amount of! I will be controlled.

In this way, if the ammonia supply amount is increased according to the difference between the actual denitrification rate and the target denitrification rate, the denitrification rate will reach the target value in a short time. FIG. 2 is a graph showing the relationship between engine operating time and denitrification rate, and compares the conventional method and the method according to this embodiment. As mentioned above, in the conventional method, the ammonia supply amount is determined from the NOx concentration of the denitrification equipment population and the exhaust gas amount, so the ammonia supply amount is generally determined based on the design denitrification rate (for example, 85
%). Therefore, as shown by @ in the figure, according to the conventional IIJ control method, it takes a long time for the NOx removal rate to rise, and in this example, it takes about 3 hours to reach the designed NOx removal rate. On the other hand, according to the control method according to this embodiment, the ammonia supply is as shown in (■), so the rise in the NOx removal rate is extremely quick as shown in (■), and in this example, the designed NOx removal rate is reached in about 30 minutes. It has been reached. Therefore, the ammonia denitrification device can be used even in equipment that is repeatedly operated and stopped, and the expected denitrification rate can be obtained relatively stably.

Next, when the denitrification rate reaches the target value, the detector 5 at the denitrification equipment outlet stops, and the detector 4 detects the No.
Switch to concentration only measurement. In the example, there are two flow rate detectors.
Although the case of one unit is shown, it is also possible to control the sampling while switching the sampling. Then, this detection signal x3 and the detection signal x1 of the exhaust gas l are combined into a calculation element 8.
The calculation result is sent to the controller 9, and the opening degree of the valve 6 is adjusted so that ammonia matching the designed denitrification rate is supplied.

[Effects of the Invention] According to the method for controlling an ammonia denitrification device according to the present invention,
Since the ammonia supply amount is increased based on the difference between the actual NOx removal rate and the target value immediately after the engine starts operating, the rise time of the NOx removal rate is significantly shortened compared to the conventional method. be.

[Brief explanation of the drawing]

FIG. 1 is a block diagram explaining one embodiment of the present invention, and FIG.
The figure shows the relationship between the operating time of the engine and the denitrification rate, and is a graph for comparing the same example and the conventional example. ! -Control device, 4-N in the exhaust gas at the inlet of the ammonia denitration equipment
A detector that measures Ox 111 degrees; 5-A detector that measures NOx concentration in the exhaust gas at the same outlet; 8-A calculation element that calculates the denitrification rate. Patent Applicant: Niigata Iron Works Co., Ltd. Agent/Patent Attorney: Norihiro Nishimura, First cylinder 1 figure removal Fi4 device 7B, Yukiyoshi

Claims (1)

[Claims] In a control method for an ammonia denitrification device that reacts NO_x in the exhaust gas emitted by the engine with ammonia adsorbed on a catalyst, the NO_x concentration in the exhaust gas at the inlet and outlet of the ammonia denitrification device is measured at the start of engine operation to determine the denitrification rate. A method for controlling an ammonia denitrification apparatus, characterized in that the amount of ammonia supplied is increased based on the difference between the denitrification rate and a target denitrification rate.