JPH07328412A - Operation of gas producing equipment - Google Patents

Abstract

PURPOSE:To provide a load setting method capable of making an operating load changing plan for minimizing the wasteful discharge of gas, etc., and improving production efficiency in a gas producing plant such as plural oxygen plants. CONSTITUTION:A gas is produced by plural gas producing plants 1 in accordance with a gas production plan prepared by a computer 7. The gas production equipment is operated to adjust the balance between the production of gas and the necessary supply to the demand 3 by discharging the gas. The load limiting time for limiting the change of load is predetermined to operate the plants under constant load, a load change limiter to limit the load change during the determined load limiting time is provided to each of the plants, and a gas production plan satisfying the load limiting time and necessary supply is prepared by the computer 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating a gas production plant, and more particularly to a method of operating a gas production facility suitable for an oxygen plant in an oxygen gas supply and demand system having at least two oxygen plants. .

[0002]

2. Description of the Related Art Generally, a large-scale steel plant, a chemical plant, or a factory that demands a large amount of acid nitrogen (hereinafter referred to as a steel plant, etc.) generally has a plurality of oxygen plants 1 installed side by side. is there. A typical flow of such an oxygen gas supply and demand system is shown in FIG. In FIG. 1, an oxygen plant 1 compresses and purifies the atmosphere while passing through a raw material air compressor, an impurity purifier, and a main heat exchanger, which are not shown in the figure, as is well known.
Cool and introduce into a rectifying column for air separation. In the rectifying cylinder, nitrogen gas having the lowest boiling point is taken out from the cylinder top part, argon gas is taken out as a product from the cylinder bottom part, and oxygen gas is taken out from the bottom part as a product by using the rectification principle. It is being sent to the oxygen demand factory 3.

In general, the gas demand amount of each oxygen demand factory 3 usually greatly fluctuates in a short time depending on its operation plan and operation condition. On the other hand, the load adjustment speed of the oxygen plant 1 is extremely slow and usually takes 30 minutes to 1 hour. The fluctuation range is 8 with respect to the oxygen supply capacity.
It is said that the limit is about 0% reduction, and that once the load is changed, it usually takes about 3 to 4 hours until the air separation rectifying cylinder can stably change the load again. There are various restrictions.

Therefore, for the purpose of absorbing such demand fluctuations of oxygen gas, several high-pressure gas holders 4 are installed in the feed path 2 to store the excess gas, which can be stored in a short time of several tens of minutes. Fluctuations in demand are smoothed. In such an oxygen demand system, in order to match the supply amount of the oxygen plant 1 and the usage amount of the oxygen demand factory 3, the demand plan totalization transmission mechanism 6 for transmitting the factory demand plan to the oxygen plant 1
Therefore, it is necessary to operate the oxygen plant 1 in a planned manner.

Generally, as a method of operating the oxygen plant 1, the required supply amount plan is obtained from the demand plan which is input from the oxygen demand factory 3 and aggregated and transmitted by the demand plan aggregation and transmission mechanism 6. Then, this plan is categorized into long-term changes of at least several days and medium-term changes of several hours, and the oxygen plant 1 that satisfies the average value in the section where the demand does not seem to change in the long term. The cardinal number of is determined as the operating cardinal number. After that, the oxygen supply pressure of the plant is monitored by the pressure detection mechanism 5 of the high-pressure gas holder, and when the medium-term fluctuation of the demand occurs and the holder pressure tends to rise and fall, the load of the oxygen plant 1 is adjusted. The holder pressure was kept above the upper and lower limits.

At this time, the following method is known as a conventional method for determining the operation plan of the oxygen plant 1 using the computer 7 or the like. For example, as in Japanese Examined Patent Publication No. 1-28313, focusing on the oxygen gas generation efficiency of each oxygen plant 1,
For long-term fluctuations in demand, a linear programming method is used to combine the operation and shutdown plans of multiple oxygen plants, and for medium-term fluctuations, non-linear planning is used to adjust the plant load. , There is a method to determine the operation plan of the oxygen plant that consumes the least power.

Further, as a method for adjusting the load of each oxygen plant against medium-term fluctuations, for example, Japanese Patent Laid-Open No.
As in Japanese Patent Publication No. 199882, an upper limit, an upper limit, a lower limit, and a lower limit are set in the state value of each process using an expert system, and the time from when the upper limit is exceeded to when the upper limit is exceeded is a past fixed time actual state. Several concrete methods have been proposed, such as a method of predicting from values and reflecting them in plant control.

[0008]

As described above, in the conventional method for determining the operation plan of a plurality of oxygen plants by using a computer or the like, a nonlinear programming method or an expert system is used. For example, a computer program has only a method of performing complicated calculations, and a large-scale computer system is required to issue an operation instruction to an oxygen plant in a short processing time that is realistic. Further, even in these conventional methods, it is necessary for the operator to adjust the load change limit time of the plant in advance and the system requires human intervention.

Therefore, as a practical method for changing the loads of a plurality of plants without using a large-scale computer system, a plant having the lowest efficiency and taking a lot of time to change the loads is set as a base load base. The priority is fixed in the order in which it is easy to change the load, and the plant load is changed in this order. Generally, a fixed planning method is adopted.

In this case, for example, the three oxygen plants 1 having the feeding performances as shown in Table 1 below are used in the oxygen demand factory 3
A method of making an operation plan by the conventional method in the demand and supply system as shown in FIG. Hereinafter, in order to simplify the description, a value obtained by subtracting the minimum load from the load of the plant will be referred to as a load adjustable amount, and this will be used for description. That is, the load changeable amount of the plant capable of adjusting the load to 80 to 100% is 0 to 20%.

[0011]

[Table 1]

Therefore, if the load change order is determined in the order of 3 → 2 → No. 1 oxygen plant 1 and the required feed rate as shown in FIG.
After reducing the load to 0% (0% in the figure), the No. 2 oxygen plant will be reduced to 80% load (0% in the figure). At this time, it is not possible to change the load of Nos. 1 and 2 in response to the subsequent increase in demand within the load change limit time, so the shortage of oxygen is vaporized from the liquefied oxygen that was stored in the liquefied oxygen tank in advance. Need to send by. 100% after 4 hours when the rectifying column of No. 3 oxygen plant stabilizes
By returning to (30% in the figure), vaporization and feeding can be stopped. However, vaporization and feeding of liquefied oxygen is a waste of cold, which leads to an increase in the total feeding cost. The energy loss due to this is much larger than the difference in production efficiency between oxygen plants. Therefore, if the load of the No. 3 oxygen plant is not reduced as shown in FIG. 3 in anticipation of this increase in load, there is a problem that a large amount of gas is diffused and the feeding cost is similarly increased.

The present invention provides a load setting method for an oxygen plant capable of making a load change plan for a plurality of oxygen plants so as to minimize waste such as gas emission and improve production efficiency. To aim.

[0014]

In order to achieve such an object, the invention according to claim 1 produces gas by a plurality of gas production plants according to a gas production plan prepared in advance by a computer, and produces the gas. In a method of operating a gas production facility that adjusts the balance between the amount of produced gas and the required supply to the demand destination by means of gas diffusion, in order to operate the gas production plant at a constant load, change of load is limited. A load change limiter for limiting the load fluctuation at the predetermined load limit time is provided in each of the plurality of gas production plants, and the condition of the load limit time and the required supply amount is set. A gas production plan satisfying the above conditions is created by the computer.

The invention of claim 2 sets a plurality of combinations in which the load change order of the plurality of gas production plants is changed while satisfying the above conditions, and the most gas emission among the plurality of set combinations is set. It is characterized in that a combination with a small amount is acquired by the computer, and the gas production plan is acquired by the computer according to the acquired combination.

[0016]

According to the first aspect of the present invention, when the gas production plant is stopped, the gas load is limited by the load limiter for the load limiting time in consideration of the fact that the gas cannot be produced until a fixed time elapses. This allows the load to be changed immediately when the load limit time is exceeded, and
An operation plan with the highest production efficiency in such a load limited state is created by a computer.

According to the second aspect of the invention, the feasible load fluctuation order is simulated by a computer to create an operation plan.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

An oxygen supply and demand system to which the present invention is applied is shown in FIG. 4 that are the same as in the conventional example of FIG. 1 are denoted by the same reference numerals, and the description thereof will be briefly described.

In FIG. 4, the oxygen plant 1 rectifies raw material air in a rectifying cylinder to separate oxygen, nitrogen and argon. The oxygen gas supply path 2 has an oxygen compressor that draws out oxygen gas from the oxygen plant 1 and raises the pressure, and an oxygen gas flow rate instruction adjusting mechanism, and supplies oxygen gas to a customer.

The high pressure gas holder 4 and the pressure detection instruction mechanism 5 are provided in the oxygen gas supply path 2. The oxygen demand plan aggregation and transmission mechanism 6 transmits the oxygen demand plan of the oxygen demand factory 3 to the oxygen plant 1. The computer 7 formulates an operation plan of the oxygen plant that matches the oxygen demand plan. The load change limiter 8 limits the load change time of the oxygen plant and maintains a constant load for at least the specified time.

In such an oxygen supply and demand system of FIG. 4, the load change limit time of each oxygen plant 1 is defined in advance. Further, the timing of changing the load of the oxygen plant 1 is limited to when the load changing restriction is released and when the required feed amount changes.

Since there are nPn cases of all load change orders that can be taken by the n plants, the load of the plant that surely satisfies the necessary feed amount and the load change limit is set for all of these cases. It is set in the computer 7. The computer 7 determines the case with the smallest emission amount among the set cases as the operation plan of the oxygen plant 1.

A concrete calculation procedure executed by the computer 7 is shown in FIG.

Prior to the preparation of the operation plan, the operator inputs the load limits of the plurality of oxygen plants 1, that is, the load limit time and the load limit amount (expressed in%) to the computer 7 from the keyboard or the like (S10).

Next, the operator inputs the required supply amount at each time into the computer 7 (S20).

When the initial data required for such an operation plan creation plan is input, the computer 7 finds a plurality of load change amounts that satisfy the required supply amount at the time when the load limit time is exceeded. More specifically, the first combination is selected from the combinations of load change orders that are uniquely determined by the number of oxygen plants 1, and the load is sequentially changed in a simulated order in the order of the combination, and each time point is changed. The load of (S3
0). At this time, it goes without saying that the conditions are added so that the total gas production amount of each oxygen plant becomes equal to or more than the required supply amount at that time.

In this way, the load fluctuation amount is given,
The surplus emission amount is calculated by subtracting the required supply amount from the gas production amount (S40).

In this way, the load change order of the oxygen plant 1 is sequentially changed, and the gas emission amount of the combination is calculated. Further, the calculated gas emission amount is compared with the minimum gas emission amount calculated so far, and the combination of the minimum gas emission amount and its change order and the load variation amount are detected (S40 to S80). Loop processing).

When the load change order and the load change amount when the minimum gas emission amount is obtained in this way are detected, the computer 7 creates an operation plan using these data (S
90). This procedure is the same as the conventional processing in which the operation data is fixed, and detailed description thereof is omitted.

FIG. 5 shows an example in which an operation plan is prepared in accordance with such a processing procedure when the same required supply amount as in FIG. 2 is given. If the present invention is applied, it will be a fixed correspondence to the conventional one, and from the 6 load change orders that can be taken by 3 plants, the order of 2 → 3 → Unit 1 or 2
→ 1 → Select the load change order of Unit 3 and set the load of No. 2 oxygen plant to 80% (0% in the figure) at 0 o'clock, and maintain the load of No. 1 and 3 plants. Build

According to this method, although the oxygen gas becomes excessive for 0 to 3 hours to cause gas emission, it is possible to make an operation plan with a minimum emission amount, which always satisfies the required feed amount. As a result, when the load change order is fixed until now, and the load is changed through human judgment, vaporization and delivery of liquefied oxygen, wasteful oxygen emission, and excessive load change are performed. On the other hand, in the present example, good results were obtained in that the vaporization and feeding of the liquid did not have to be carried out, and the emission amount could be reduced.

Further, in the present embodiment, the feed gas of the oxygen plant 1 is limited to the oxygen gas, but it is also possible to feed the gas such as nitrogen and argon generated together with oxygen in the plant to the factory for use. Can be used as well. Furthermore, it can also be used when planning the operating base of an oxygen plant with respect to long-term fluctuations in oxygen gas demand.

As described above, in this embodiment, in order to make a load change plan for a plurality of oxygen plants 1, each oxygen plant 1 is provided with the load change limiter 8 for limiting the load change time, The load change limit time of the oxygen plant 1 is defined in advance. Further, the timing of changing the load of the oxygen plant 1 is limited to the case where the load change restriction is released and the case where the required supply amount changes. In this case, for the case of nPn load change orders that can be taken by n plants, the computer 7 sets the load of the plant that satisfies the required feed rate and the load change limit by trial and error. The operation plan of the oxygen plant 1 is the case with the smallest emission amount.

As a result, as compared with the conventional operating procedure in which the load change order is fixed in the related art, excessive emission and vaporization and supply of liquefied oxygen due to insufficient supply are prevented. In addition, the load change time limit is the actual load change order of the plant, and until the next load change can be implemented after the rectification of the air separation rectification cylinders in each plant is stable, Since it is fixed, it is possible to minimize the number of load changes and perform rectification separation in the optimum state of the rectifying cylinder for air separation, and operate stably without reducing the product purity of oxygen, nitrogen, etc. it can.

Further, by these means, it is possible to plan the optimum feed amount according to the required feed amount while suppressing the reduction of the product gas separation efficiency and the yield, and it is possible to arrange a plurality of oxygen plants 1.
It is possible to drive using the ability of the.

[0037]

As described above, according to the first aspect of the present invention, since the amount of emission can be minimized, the production efficiency can be improved.

According to the second aspect of the present invention, the production plan having the highest production efficiency can be drafted by the computer without human intervention.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing a conventional production facility.

FIG. 2 is an explanatory diagram showing an example of an operation plan.

FIG. 3 is an explanatory diagram showing a surplus emission amount.

FIG. 4 is a configuration diagram showing a production facility according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing an excess emission amount according to the embodiment of the present invention.

FIG. 6 is a flowchart showing a processing procedure of the computer 7 according to the embodiment of this invention.

[Explanation of Codes] 1 oxygen plant 2 oxygen gas supply route 3 oxygen demand factory 4 high pressure gas holder 5 pressure detection mechanism 6 demand plan aggregation transmission mechanism 7 computer etc. 8 load change limiter

Claims (2)

[Claims] 1. A gas is produced by a plurality of gas production plants according to a gas production plan created in advance by a computer, and the balance between the production amount of the produced gas and the required supply amount to the demand destination is calculated. In a method of operating a gas production facility that adjusts by diffusion, in order to operate the gas production plant at a constant load, a load limit time for limiting a change in load is set in advance, and a load fluctuation at the set load limit time is set. A load change limiter for limiting is provided in each of the plurality of gas production plants, and a gas production plan that satisfies the conditions of the load limit time and the required supply amount is created by the computer. how to drive. 2. A plurality of combinations in which the load changing order of the plurality of gas production plants is changed while satisfying the conditions are set, and a combination with the smallest gas emission amount among the plurality of set combinations is set. The method of operating a gas production facility according to claim 1, wherein the gas production plan is acquired by the computer, and the gas production plan is acquired by the computer according to the acquired combination.