JPH03237196A - Operation of dehydration apparatus for city gas - Google Patents

Abstract

PURPOSE:To obtain a dehydration apparatus free from influence on the quality of city gas and achieving high regeneration efficiency by inserting a pressure regulation valve between an adsorbing apparatus and a spherical gas holder and keeping the pressure difference between the inlet side and the outlet side of the valve at a definite level by the regulation valve. CONSTITUTION:A pressure regulation valve is placed between an adsorbing apparatus and a spherical holder and the pressure difference between the inlet side and the outlet side of the regulation valve is controlled to a definite level between 1.5 and 2.5kg/cm<2>. The regulation of the pressure difference to a definite level is carried out by using a self-actuating governor, a governor provided with a regulation mechanism having a motor, etc., a control valve provided with a pneumatic actuator, a control valve provided with a motor, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of operating a dehydrator in the production and supply of city gas.

[Prior Art] Dehydration equipment used in the production and supply of city gas is used to reduce the moisture content in the produced city gas and lower the dew point of the gas.

This is because moisture condenses in gas pipes and valves during rain and causes corrosion, which then freezes and causes damage to pipes and equipment.

Therefore, most places that have equipment for producing city gas by decomposing petroleum-based raw materials also have dehydration equipment.

There are two main methods for removing moisture from gas: cryogenic separation method and adsorption method. In cryogenic separation method, the dew point of the gas pressurizer is limited to 2°C, and the temperature drops below 2°C. If this happens, moisture will condense and cause corrosion problems. Therefore, an adsorption method with high dehydration efficiency can be considered, but this method has the following drawbacks.

In the adsorption method, water is adsorbed by the adsorbent, so it is necessary to replace or regenerate it after a certain period of time. Of course, replacing the adsorbent is a very time-consuming task, and regeneration gas is required for regeneration. Regeneration gas can be released into the atmosphere or used for separate purposes.
Both methods are dangerous and costly, and cannot be used as city gas production equipment.

Furthermore, if the dew point is lowered to a level that does not cause condensation in the spherical holder, the pressure in the supply pipe will be reduced, so the dew point will drop significantly and the pipe will become overly dry, causing rust and other deposits in the pipe. This will cause a supply failure at a peeling valve, etc.

That is, it is undesirable for the supply conduit to become too dry.

In the end, there was no effective means to prevent condensation on the spherical holder. Therefore, corrosion of the lower part of the spherical holder becomes a big problem because the stored material is flammable.

Therefore, in order to eliminate these drawbacks, the present applicant has devised a method for removing moisture in the gas by adsorption when the gas is introduced into the spherical holder, and when the gas is supplied from the spherical holder, the supplied gas They discovered an operating method for regenerating the adsorbent, and have also applied for a patent. This method not only eliminates the need for gas for regeneration, but also does not require any special operation for regeneration.

[Problems to be Solved by the Invention] However, it has been found that the above method has the following drawbacks.

First, no pressure reducing valve is installed between the spherical holder and the adsorption tower.
If the adsorption tower is regenerated with the same pressure in the spherical holder, at the beginning of the regeneration (when the pressure in the spherical holder has not yet decreased much), there is no difference in pressure from that during adsorption, and most of the moisture is removed. It does not desorb and the regeneration efficiency becomes very poor. Therefore, in the case of such a method, a heat exchanger is provided between the adsorption tower and the spherical holder, and regeneration is performed using the heated gas. This requires additional energy and costs more.

In order to prevent this, a method can also be considered in which a pressure reducing valve is provided between the spherical holder and the adsorption tower to reduce the pressure of the gas and then introduce it into the adsorption tower. However, this method also had the following problems.

When the gas passes through the adsorption device, not only the moisture in the city gas but also a small amount of hydrocarbons are adsorbed. However, there was no problem as the hydrocarbons were also regenerated and entrained along with the water during delivery. Hydrocarbons in gas, especially butane, are more easily adsorbed and desorbed than moisture and the like. Therefore, there is a possibility that what is gradually adsorbed will be released in a short period of time. In addition, butane has a high calorific value, and even a small amount causes fluctuations in the calorie content of city gas.

Therefore, at the beginning of the regeneration process, there was a risk that high-calorie gas would be supplied during the rain.

Therefore, there has been a demand in this industry for a method of operating a dehydrator that does not affect the quality of city gas and has good regeneration efficiency.

[Means for solving 11ff 1 In view of the above-mentioned current situation, the inventor has conducted extensive research and found that
The method of the present invention has been completed, and its feature is that it uses an adsorption dehydrator installed between the spherical holder and the gas compressor, and the gas compressed by the gas compressor is When the gas is introduced into a spherical holder, moisture in the gas is adsorbed and removed, and when the gas is supplied from the spherical holder to consumers, the adsorbent is regenerated using the supplied gas. A pressure regulating valve provided between the spherical holder and the spherical holder adjusts the pressure on the secondary side of the valve.

Here, the spherical holder refers to a spherical storage tank for storing produced city gas, and the gas compressor refers to a device of any type that boosts the pressure of gas produced at low pressure. good.

An adsorption type dehydrator is one in which gas is passed through a tower filled with an adsorbent, and moisture is adsorbed and removed by the adsorbent.

Once this adsorbent has adsorbed a predetermined amount of moisture, it will no longer adsorb any more moisture, so a regeneration process is necessary. The regeneration process refers to desorbing water from the adsorbent. There are two methods of regeneration: a thermal swing method and a pressure swing method, both of which require regeneration gas.

The thermal swing method is a method in which the adsorption capacity is greater at low temperatures than at low temperatures, so it is adsorbed at low temperatures and desorbed by raising the temperature.

The pressure swing method is a method in which adsorption is performed at high pressure and desorption is performed at low pressure, since the adsorption capacity is greater at high pressure than at low pressure.

The regeneration gas is passed through at high temperatures and/or low pressures to entrain the moisture with the regeneration gas.

Normally, this regenerated gas is released to the atmosphere or used for a separate purpose, and cannot be mixed with the product gas of the facility or made into a product, since it is necessary to obtain a dehydrated gas. This is because the device is used for

The method of the present invention is completely different from conventional methods in that the gas produced by regenerating the adsorbent is used as a product.

This will be explained in detail below.

The production gas from the production device passes through a dehydration device, has its moisture removed by the adsorbent, and is stored in a spherical holder. Therefore, gas with a low dew point (usually below -20° C. under pressure) is stored in the spherical holder.

When supplying city gas during rain from this spherical holder, the gas from the holder is introduced into a dehydrator, the adsorbent is regenerated by the gas, and gas containing moisture is supplied into the rain. The regeneration method in this case is a pressure swing method because the pressure is reduced on the exit side of the spherical holder, but it is also possible to add a thermal swing method by raising the temperature of the gas a little at the same time.

When regenerating with product gas in this way, the actual problem is that gas without moisture removed will be released into the rain.
This is not a problem because the pressure is very low, and it will be more complete if a normal cryogenic separation type dehydrator is installed upstream of the above-mentioned adsorption type dehydrator. In fact, if there is not much difference between the compressor outlet side and the rain supply pressure, such a cryogenic separation type dewatering device is considered necessary.

Next, a pressure control method during this regeneration will be explained.

In the first method of the present invention, a pressure regulating valve is provided between the adsorption device and the spherical holder, and the regulating valve is controlled by the pressure on its primary side, so that the differential pressure at the valve is 1.5 to 2. .5kg/cm2
This is to maintain a constant value between .

The reason for doing this is as follows.

The pressure inside the adsorption tower is approximately the same as that of the spherical holder at the end of the adsorption process (pressure feeding process to the spherical holder).

In addition, the supply pressure during rain is determined by each gas supply station depending on the distance to the consumer and the amount, but in places that have a spherical holder, it is usually around 2 to 3-/cm2. . Therefore, at the exit side of the spherical holder, the supply pressure (for example, 2
kgloJ). At this time, if the adsorption tower is 7 kg/cd, the differential pressure with the regeneration gas (i.e., the supply gas) will be 5 pupils/cm2, and in the conventional method, the adsorbed butane etc. would be desorbed at once. This causes the gas to become more calorie-dense.

Therefore, in the present invention, a pressure regulating valve is provided between the spherical holder and the adsorption tower, thereby preventing the adsorption tower from being rapidly depressurized, and also preventing or reducing temporary desorption of butane, etc. It is something.

Various methods can be used to adjust the pressure. For example, there is a method of controlling the pressure so that the differential pressure between the primary side and the secondary side of the pressure regulating valve is always kept constant. There are various ways to keep the differential pressure constant, including a governor with an adjustment mechanism such as a self-cutting governor motor, a control valve with an air-operated actuator, and a control valve with a motor. In this way, a sudden pressure difference does not occur, so butane and the like are not desorbed in excess of the adsorbed amount, and fluctuations in calories are suppressed.

Instead of continuous control using the pressure on the primary side, stepwise control is also possible. For example, manually step by step 2
The next pressure may be switched. At the beginning of the regeneration process, a high pressure (for example, 5 kg/cd) is set, and after a certain period of time, the pressure is set again to a low pressure (for example, 3 kg/ej).

Of course, this stepwise control may also be performed by detecting the primary pressure.

The positional relationship between the spherical holder and the dehydrator may be arbitrary, as long as the spherical holder is arranged so that it can pass through the dehydrator when entering and exiting the spherical holder. Therefore,
The spherical holder may be installed in a so-called branch pipe or may be of a passing type.

Next, a case will be described in which the spherical holder is located not at a gas production facility but at a gas supply station remote from the gas production facility. In this case, it is desirable that the adsorption dehydrator be installed at the gas supply station, similar to the spherical holder. The reason for this is that the entire amount of manufactured gas does not pass through the spherical holder, and a portion of the gas sent from the manufacturing plant to the supply station does not pass through the spherical holder and is directly supplied into the rain. In this case, if the manufacturing facility is equipped with an adsorption dehydrator, a dehydrator must be designed to allow the entire amount to pass through, resulting in a large-sized device. Furthermore, the conduit extending from the manufacturing facility to the supply facility over a distance (usually several kilometers to several tens of kilometers) becomes over-dried, which is undesirable.

If an adsorption dehydrator is installed at a supply point and requires manpower to operate, labor costs will increase. This is because supply stations are usually unmanned, and the dehydration equipment requires human labor, which is wasteful. Therefore, it is necessary to operate the dehydration device remotely. This is easiest to do by installing a dedicated line and operating it electrically, but
In remote areas, it is practically impossible to install such a line. Therefore, a communication system using telephone lines such as NTT is suitable. This converts the intention of the manufacturing plant into a signal that can be used over a telephone line, such as voice or digital signal, and sends it to the supply center via the telephone line, and the dewatering equipment is operated by the signal. Conversely, from the dehydration equipment side, signals from various detection devices are similarly sent to the manufacturing plant side, where they are used for operational purposes. If the pressure regulating valve is automatically controlled, it can be operated without any problems.

As explained in the thermal swing method above, it is preferable to use heated gas for regeneration, but if an adsorption dehydrator is installed at a supply station, waste heat is Since this is not possible, it is convenient to use a general-purpose hot water boiler.

〔Example] ! Figure @1 is a flow sheet showing an example of the present invention. The production gas is pressurized by compressor 1 to 8K in this example.
g/cII) and introduced into the cryogenic separation type dehydrator 2 and dehydrated until the dew point becomes about 2°C.

At this time, the production gas valve 3 and the dehydrator valve 4 are opened, and the supply valve 5 is closed.

The produced gas that has passed through the dehydrator valve 4 is further dehydrated by the adsorption dehydrator 6, and its dew point becomes 20° C. or lower under pressure. At this time, the regeneration control valve 7 is closed, and the check valve 8
The gas is introduced into the spherical holder 9 and stored there.

Therefore, the dew point of the gas in the spherical holder 8 is -20° C. or lower under pressure, and there is no fear of moisture condensation.

Of course, in winter or in cold regions, the adsorption type dehydrator 6
You can lower it to a lower dew point.

Next, when gas is to be supplied during rain, the production gas valve 3 is closed and the supply fp5 is opened. At this time, the gas is
cannot pass through, and is released at the same time as the regeneration viglI
Passes through valve 7. The gas whose pressure is reduced by a certain value (here, 2 kg/cj) by this valve 7 enters the dehydrator 6. The dew point of this gas is lower due to the reduced pressure.

The gas introduced into the dehydrator 6 regenerates the adsorbent, that is, removes the adsorbed moisture.

The dew point of the gas on the outlet side of the dehydrator 6 is 0 to 2° C. under pressure because it contains moisture. However, when you go out in the rain, the pressure is lower, resulting in a lower dew point. Therefore, it can be said that there is no problem of condensation in the pipes during rain. The gas leaving the dehydrator 6 finally passes through the governor 11 that determines the supply pressure, and is kept at a constant supply pressure (here, 2.5 kg).
/cd) and is sent out in the rain.

As the pressure in the spherical holder 9 decreases, the pressure is detected and the opening degree is adjusted by the actuator 12 so that the differential pressure is always kept at the constant value, so that detachment is performed in a well-balanced manner.

Furthermore, as another example, it is also possible to provide a gas heater at an intermediate position between the dehydrating device 6 and the spherical holder 9. That is, when regenerating the dehydrator 6, the temperature should be slightly raised (30 to 50
This is because regeneration will be more complete if the gas is used at a temperature of This gas heater may be of any kind, such as an electric one or a heat exchanger that utilizes residual heat from hot water or the like.

FIG. 2 is a schematic flow sheet showing the case where the present invention is utilized at a supply station separate from a gas production plant. In this example, the gas compressor 1 is located at the manufacturing site, and the adsorption type dehydration bag W
6 is on the supply side. Therefore, over-dried gas does not pass through the conduit 13 from the manufacturing facility to the supply facility, and only normal dehydrated gas that is not dehydrated or has a dew point of up to about 2° C. under pressure passes through. This eliminates the problem of overdrying of the conduit.

The relationship between the adsorption type dehydrator 6 and the spherical holder 9 and the operating method are the same as those shown in FIG.

Furthermore, starting, stopping, and operating the dehydration bag M6 are all performed using a telephone line.

[Effect of the invention] According to the operating method of the present invention, there are the following effects.

■ There is no moisture condensation on the spherical holder, so there is no need to worry about corrosion of the holder.

■ No regeneration gas is required, and there is no part of the product or manufacturing loss.

■ Separate running costs for adsorption and regeneration are not required. However, if a gas heater or the like is used, this is necessary but can be adjusted depending on the effectiveness.

■ Since the supply pipe does not become overly dry, accidents such as valve clogging do not occur.

■ Since there is no rapid depressurization in the adsorption tower, there is no rapid desorption of butane, etc., and there is almost no change in gas calories.

1... Compressor 3...Production gas valve 5... Supply valve 7...Regeneration control valve 9... Spherical holder 11.--Governor 13... conduit 2...Cryogenic separation type dehydration equipment 4...Dehydrator valve 6... Adsorption type dehydration device 8...Check valve 10...Holder valve 12...actuator

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing an example of the present invention,
FIG. 2 is a flow sheet showing another example.

Claims (1)

[Claims] 1. An adsorption dehydrator installed between a spherical holder and a gas compressor is used, and when the gas compressed by the gas compressor is introduced into the spherical holder, the gas is When gas is supplied from a spherical holder to a consumer by adsorption and removal of water, the adsorbent is regenerated by the supplied gas. A valve connects the primary and secondary sides of the valve.
A method for operating a dehydrator in city gas production and supply, characterized by controlling the differential pressure on the next side to a constant value between 1.5 and 2.5 kg/cm^2. 2. An adsorption dehydrator is installed between the spherical holder and the gas compressor, and when the gas compressed by the gas compressor is introduced into the spherical holder, the water in the gas is adsorbed and removed. When gas is supplied to consumers from a spherical holder, in the method of regenerating the adsorbent using the supplied gas, the pressure regulating valve provided between the adsorption device and the spherical gas holder is used to control the pressure of the valve. A method for operating a dehydrator in city gas production and supply, characterized by manually or automatically changing the secondary side pressure.