JPH0228633B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to city gas production equipment.

City gas has various components depending on its manufacturing method, raw materials, etc. Examples include natural gas, a mixed gas of LPG (liquefied petroleum gas) and air, and other petroleum cracking gases.

In the case of city gas, it contains many components,
Moreover, there are many different manufacturing methods and types.

There would be no problem if such city gas could be easily replaced with a gas that is easy to produce or obtain and is inexpensive, but this is usually not possible because the flammability ranges of the gases are different. This combustion range is determined by the properties of the gas, and is influenced by the combustion rate, specific gravity, etc. of the gas. If this combustion range does not match your gas appliance,
It is extremely dangerous as it does not burn properly. Therefore, the recent gas conversion (change in combustion range) carried out by major gas companies involves the work of upgrading all gas appliances in each household to match the changed combustion range. However, this is possible only in special companies, and not in many ordinary gas companies. Therefore, it is no exaggeration to say that places that supply city gas will not change their combustion range.

This city gas often consists of hydrogen, carbon dioxide, carbon monoxide, etc. In the early days of gas supply, gas was produced from coal;
Because its composition was like this, it has remained unchanged even after the raw materials were replaced with petroleum-based ones.

Recently, efforts have also been made to improve efficiency by mixing conventional gas with as much LPG as the combustion range allows to heat it up and then diluting it with air. The purpose of this is to lower the production cost of city gas, and the equipment for this purpose is called a heat adjustment device.

The prior art will be explained below with reference to FIG.

The city gas production facility 1 is composed of a heat adjustment device 2, a low-pressure water holder 3, a pressure feeding device for a reciprocating compressor 4, and a piping system connecting them. Check valve 5 downstream
A high-pressure spherical holder 6, which is a city gas storage tank, is provided through the holder.

In the city gas production facility having the above configuration, first the raw material gas is passed through the blower 7 to the heat adjustment device 2.
The mixer 8 is equipped with a calorific value controller 1 having a detection section upstream of the low-pressure water holder 3.
Based on the signal from 0, the control valve V3 installed in the pipe is controlled via the flow rate controller 9, and the amount of heat is within a range that satisfies the predetermined calorific value as city gas.
Appropriate amounts of LPG and air are introduced to form a substantially uniform state of so-called city gas, and the mixed gas is sent to the water holder 3 and temporarily stored,
The gas is forced into the high-pressure spherical holder 6 by the pressure feeding device 4 . This is a general method, and although the details may differ, this method is basically adopted everywhere.

In this case, the reason why the low-pressure water holder 3 is provided in the middle is to maintain a balance in the flow rate between the amount of gas from the heat adjustment device 2 and the amount pumped by the compressor 4. This is to detect the gas amount with the level switch LS and control the capacity control valve V4 of the compressor 4 so that the level is within a certain range, and to prevent the pulsation of the compressor 4 from affecting the low pressure heat amount control device. It is also for the purpose of

Moreover, if this water holder 3 is not provided, if the suction of the compressor is too strong, a negative pressure will be created and water or air will be sucked from the water seal or the like. Conversely, if the compressor suction is insufficient, the pressure on the low pressure side will rise, breaking the water seal and causing gas to leak out of the system. Especially when it comes to flammable materials,
If the air is sucked in, it will create explosive air, and if it escapes from the system, it may cause a fire or other danger.

Since the demand for city gas fluctuates greatly within a day, it is necessary to adjust the operating capacity accordingly, but since the compressor 4, which is the pressure feeding device, is a reciprocating compressor, its capacity adjustment is necessary. Since this can only be done in stages, instantaneous pressure fluctuations occur at the boundaries of each stage, as well as pressure fluctuations associated with the pulsation inherent in the reciprocating type as described above.

These pressure fluctuations have a significant adverse effect on the maintenance of the calorific value of the gas from the calorific value regulator, since the calorific value regulator provided in the calorific value regulator 2 is extremely sensitive to pressure fluctuations.

Therefore, in general, a water holder is required to have a capacity of about 20 minutes of the equipment capacity, and 10,000
m ³ /h city gas production equipment usually has a capacity of 3000 m3/h.
It becomes extremely large, about ³ m3.

Such a low-pressure water holder 3 (hereinafter referred to as an intermediate gas holder) is expensive to manufacture and requires a large site area.

Therefore, it has been strongly desired to omit such an intermediate gas holder 3.

On the other hand, in steelworks, there was a desire to use the off-gas (by-product gas) generated in large quantities as something with high added value, rather than simply using it as fuel for the company.

Steelworks have already separated hydrogen and carbon monoxide from off-gas and used it as high-value-added chemical raw materials, but demand for these is inevitably small.
In addition, in cases where the location is favorable, such as a steelworks located adjacent to a large consumption area, a considerable amount of the fuel used is sold to city gas companies.

Coke oven gas, typically the off-gas from steel plants, is a by-product when coal is dry distilled to produce coke.It is high in calories and can be used as city gas due to its flammability, so city gas companies This is because there are advantages to purchasing this.

Another type of off-gas from steelworks is blast furnace gas, which has a low calorie content of around 700Kcal/ ^Nm3 and has a high carbon monoxide concentration, making it a gas with low utility value.There is a big demand in steelworks for the effective use of this gas. It was hot.

Therefore, the present inventors set up a technical problem of omitting the intermediate gas holder 3 in a city gas production facility where the supply amount of one or more types of raw material gases to the facility is not constant. As a technical means to achieve this problem, we conceived the idea of performing interconnected instrumentation in the gas production equipment and the compressor 4, and controlling the flow rates so that the respective gas flow rates are balanced.

In other words, in order to solve the considerable pressure fluctuations caused by pulsation and stepwise capacity adjustment, which are problems unique to reciprocating compressors, rotary compressors such as pulsation-free screw compressors and turbo compressors are used as boosters. It is possible to adopt this.

By the way, since the demand for city gas fluctuates greatly within a day, the daily operating capacity is set in advance in response to this, and it is necessary to adjust the capacity to match it. The capacity adjustment methods include bypass control, suction throttle valve control, and slide valve control when using a screw compressor, and slide valve control in addition to the former two when using a turbo compressor. There are compatible suction vane controls, but the slide valve type when using a screw compressor is the most effective in providing smooth continuous capacity control and power reduction according to the flow rate load.

Figure 2 shows a screw compressor 14 with a slide valve type capacity adjustment device based on this idea.
This shows the flow when the intermediate gas holder is eliminated by adopting .

However, even if the booster is a screw compressor with a slide valve type capacity adjustment device, the boost gas flow rate can be adjusted continuously from 20 to 30% to 100%, but from 0 to 20 to 30%. Since the range cannot be controlled, a bypass pipe 12 with a bypass control valve 11 is provided to compensate for this. In other words, 20 to 30, which is the minimum amount that can be continuously and smoothly controlled.
The capacity is adjusted by the slide valve 13 up to % capacity, and the bypass control valve 11 is opened for the capacity below that, and the capacity is adjusted by bypass.

When starting the screw compressor 14, the slide valve 13 is fully opened for no-load startup, and the bypass valve 11 is also fully opened.
The bypass valve 11 and slide valve 13 will be gradually closed.

To explain the operation, the compressor 14 is already activated and discharges 20 to 30% of the maximum discharge amount just before the production gas flow rate starts to increase from 0.
Naturally, the opening degree of the slide valve 13 at this time is the maximum. In this case, the pumping amount is still 0, so the bypass valve 11 is fully open. In other words, the bypass pipe 12 and the bypass valve 11 are designed so that 20 to 30% of the discharge amount can be completely bypassed.

When the amount of pumped gas (the amount of gas that needs to be pumped) is increased, the bypass valve 11 is gradually closed. Moreover, once the bypass valve 11 is fully closed, the opening degree of the slide valve 13 can be increased thereafter. In this case, the slide valve 13 is controlled by the low-pressure side line pressure, so when a large amount of gas is introduced into the low-pressure side line 15, the pressure increases and the opening degree of the slide valve 13 automatically changes. As a result, the discharge amount of the compressor 14 increases. That is, by adjusting the suction capacity of the compressor so as to keep the suction pressure of the compressor constant, the amount of produced gas and pumped gas is balanced.

When adopting a turbo compressor instead of the screw compressor mentioned above, the slide valve is replaced with a suction vane, and its capacity adjustment range is 70 to 100%, so the 0 to 70% portion is replaced by a bypass valve. They are essentially the same, just in a complementary form.

However, until now, realistically, intermediate gas holder 3
I have never seen or heard of a case where this was omitted. Another reason was that when the compressor was started, an unavoidable pressure shock to the low pressure side was generated.

This is because in order for the pressurized gas on the compressor discharge side to return to the suction side through the bypass piping 12 at startup, the discharge side must be filled with a certain pressure or more, and there is a time delay. The pressure on the suction side of the compressor will decrease for several seconds. This decrease in pressure is equivalent to being called a pressure shock, and is of a nature that cannot be followed by suction pressure control.

Such a pressure shock is a type of pressure fluctuation, and as mentioned above, this has a significant negative effect on the heat adjustment system. Unless this is avoided, the technical objective of the present invention of omitting the intermediate gas holder 3 will not be achieved. It is not possible.

In view of the circumstances detailed above, the inventors of the present invention have conducted further intensive research and have completed an extremely innovative city gas production facility that omits a huge intermediate gas holder, and its characteristics are as follows: However, it is a city gas production facility that mixes multiple raw material gases, and the calorific value adjustment method uses a calorific value controller to adjust the flow rate control valve of LPG or air via a flow rate controller so that the gas has the characteristics as city gas. The system is composed of a heat regulating device having a heat regulating system, and a pumping device that pumps gas from the heat regulating device to a storage tank, and the pumping device is a rotating The rotary compressor comprises a return pipe provided with an on-off valve connected to the suction side of the compressor from further downstream of a check valve provided downstream of the rotary compressor, and The main feature is that the suction capacity of the compressor is controlled by the suction pressure of the compressor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings, with reference to an embodiment in which off-gas from a steelworks is used as a raw material and a screw compressor is employed as a rotary compressor.

FIG. 1 is a schematic flow sheet illustrating one embodiment of the present invention. Two types of raw material gas before calorific value adjustment are used: coke oven gas and blast furnace gas, which are off gases from steel plants.

As for the flow, each gas is sucked by a blower 7 from the coke oven gas line 17 and the blast furnace gas line 18 and introduced into a mixer 8 which is a heat amount adjustment process. This mixer 8 has an adjusted amount.
LPG and air will be introduced. By this,
So-called city gas is produced. From this mixer 8,
It is press-fitted into the high-pressure spherical holder 6 by a compressor. A screw compressor 14 is adopted as this booster, and the compressor 14 is provided with a slide valve 13 and a bypass valve 11, which adjust the suction capacity of the compressor to the low pressure line 15 side by a pressure regulator 19. The line pressure is controlled to be constant. In addition, a return pipe 20 is provided to connect the high pressure line 16 downstream of the check valve 5 to the low pressure line 15. A return valve 21 is provided in the low pressure line of the return pipe 20. The opening and closing of the return valve 21 is temporally linked to the activation of the screw compressor 14.

In the present invention, the return valve 21 is set to open simultaneously when the screw compressor 14 is started. In this way,
The problem of depressurization on the low pressure line 15 side due to suction by the screw compressor 14 does not occur.
This is because at the same time as the return valve 21 opens, line gas from the high pressure side line 16 flows into the low pressure side line 16.
5, the problem of the time delay in the gas flowing from the bypass pipe 12 does not occur. Also, as the compressor approaches a steady state, if the return valve 21 is left open,
In order to prevent the rise in line pressure on the low pressure side and maintain a constant pressure, the control valve is designed to detect suction pressure and close.

Therefore, even when the screw compressor 14 is started, there is no pressure fluctuation on the low pressure side, and since it is a screw compressor, there is no pulsation, so the pressure in the upstream system can be controlled. There is no need for an intermediate gas holder as a so-called cushion tank to maintain a constant flow.

Of course, providing a device with a small capacity itself is not a problem since it does not impose a burden in terms of equipment costs or required area.

It is thought that this allows the advantage of the rotary compressor, which does not pulsate, to be truly utilized. That is,
In the past, it has not been possible to link such advantages to the great advantage of eliminating the need for a holder, or rather, such an idea has not even been thought of.

Additionally, for steel mills, there is an advantage in that by mixing blast furnace gas and coke oven gas, added value is added to the blast furnace gas.

In terms of raw material costs for city gas, as off-gas from steel plants, especially blast furnace gas, is also used,
It is cheaper than gas produced from regular naphtha or LPG.

The bypass piping 12 in this example would not be necessary if the screw compressor 14 could control the flow rate continuously from 0 to 100%. Furthermore, as a countermeasure against pressure shock, the return valve 21 may be one that does not detect the pressure in the low pressure line 15 and automatically closes in a certain pattern after a certain period of time. This pattern can be calculated from the pressure fluctuation characteristics for several seconds when the screw compressor is started.

In addition, the return valve 21 detects suction pressure and
It may be controlled to open automatically when the pressure falls below a certain level.

In this embodiment, meters, valves, etc. other than those mentioned above are not explained for convenience, but necessary items may be provided, and the provision of such items is not irrelevant to the essence of the present invention. be. Further, the raw material gas is not limited to off-gas, and the compressor may be a rotary compressor, and is of course not limited to the embodiments.

As explained above, the present invention is an epoch-making device that completely eliminates the need for the large-capacity intermediate gas holder, and also makes blast furnace gas highly value-added for steel plants. This is extremely beneficial for gas supply companies, as it reduces raw material costs and equipment costs.

[Brief explanation of drawings]

Figure 3 is a schematic flow sheet showing a conventional example, Figure 2 is a schematic flow sheet showing an improved idea, and Figure 1 is a schematic flow sheet showing a conventional example.
The figure is a schematic flow sheet illustrating an embodiment of the invention. 1...Gas production device, 2...Calorific value adjustment device, 3...Low pressure water holder, 4...Compressor, 5...Check valve, 6...High pressure spherical holder, 7...Blower, 8...Mixer, 9...Flow rate controller , 10...calorific value controller, 11
...Bypass valve, 12...Bypass piping, 13...Slide valve, 20...Return piping, 21...Return valve.

Claims (1)

[Claims] 1. A city gas production facility that mixes a plurality of raw material gases, in which a flow rate control valve for LPG or air is controlled by a calorific value controller via a flow rate controller so that the gas has the characteristics of city gas. Consisting of a heat amount adjustment device having a heat amount adjustment system to adjust the amount of heat, and a pressure feeding device that pumps gas from the heat amount adjustment device to a storage tank,
The pressure feeding device includes a rotary compressor installed in the middle of the gas line connecting the heat amount adjustment device and the storage tank, and a check valve installed downstream of the rotary compressor. A city gas production facility comprising a return pipe connected to the suction side and having an on-off valve interposed therein, and the suction capacity of the rotary compressor is controlled by the suction pressure of the compressor. . 2. Claim 1 uses blast furnace gas and coke oven gas as part of the raw material gas.
City gas production equipment as described in section.