JP2008232593A - Mixed gas supply device and its composition variation adjusting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mixed gas supply device suitable for stabilizing the heating value of fuel gas such as city gas, and its composition variation adjusting method. <P>SOLUTION: With the start of control, the operation start temperature T1 of a cooling device is determined first based on a variation width determination table. During operation, a filling tower internal temperature Ts is always measured by a temperature sensor S1. In the case of Ts≥T1, whether the cooling device 6 is already in operation is determined. In the stop state of operation, cooling operation is started. During cooling operation, whether the measured value Ts of the temperature sensor S1 has reached a lower limit temperature T0 or lower is determined. In the case of Ts≤T0, there is a possibility of component gas being liquefied. The operation of the cooling device 6 is thereby stopped (S107). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a mixed gas supply apparatus and a composition variation adjustment method thereof, and more particularly to a mixed gas supply apparatus suitable for suppressing a heat generation amount variation of a fuel gas such as city gas and a composition variation adjustment method thereof.

  In recent years, LNG (liquefied natural gas) satellite bases have been built with increasing demand for city gas in regions far from metropolitan areas. The LNG satellite base is a facility equipped with LNG storage tanks and vaporizers. After transporting LNG from the coastal LNG receiving terminal by lorry and storing it in the LNG storage tank, the LNG is vaporized to industrial parks and residential areas. It is for supply as city gas.

In such an LNG satellite supply system, there is a case where the calorific value fluctuation of the supply gas accompanying the start of operation of the carburetor, load fluctuation, temperature change or the like occurs. Technology is disclosed. As an improvement of the vaporizer itself, a technique for purging LPG from a purge line when the LNG vaporizer is stopped has been proposed (for example, Patent Document 1).
In addition, as a mixed gas supply device using an adsorbent, a technique has been proposed in which an adsorbent packed tower filled with activated carbon is provided on the downstream side of the vaporizer to level the calorific value (for example, Patent Document 2).

  FIG. 10 shows a conventional mixed gas supply apparatus 100 using such an adsorbent packed tower. A conventional mixed gas supply apparatus 100 mainly includes an LNG storage tank 101, a vaporizer 102 using outside air as a heating source, and an adsorbent packed tower 103. The adsorbent packed tower 103 is filled with activated carbon having a pore diameter of 2.0 to 3.0 nm. With such a configuration, the LNG supplied via the tank lorry 105 and the line 106 is temporarily stored in the LNG storage tank 101, vaporized by the vaporizer 102 to become natural gas, and further passed through the adsorbent packed tower 103. Thus, when the composition ratio of the high boiling point (heavy hydrocarbon) component is high and the gas calorific value is high on the outlet side of the vaporizer, the high boiling point component is adsorbed by the adsorbent, and the composition ratio of methane which is the low boiling point component is When the calorific value is high and the calorific value is low, the adsorbed high boiling point component is desorbed to equalize the calorific value.

JP-A-7-109476 JP 2005-273753 A

  In general, it is known that the amount of adsorbent adsorbed decreases at a high temperature and increases at a low temperature. However, regarding the calorific value adjustment method using an adsorbent, although there is a disclosure (Patent Document 2) of a technique for stably supplying natural gas by heating the packed tower to a set temperature (35 ° C.) in winter, There is no disclosure of a calorific value adjustment method over the environmental temperature range assumed in practice. The same applies to the composition fluctuation suppression technology.

As a result of intensive studies, the inventors have completed a mixed gas supply device that exhibits a high composition fluctuation suppressing effect in a wide temperature range that is assumed in practice. The gist of the present invention is as follows. That is,
The invention of claim 1 is filled with a supply line that supplies a mixed gas whose composition changes over time, and an adsorbent that is interposed in the supply line and has a characteristic that the composition fluctuation suppressing performance decreases with increasing temperature. And a means for cooling the inside of the packed tower when the temperature inside the packed tower is equal to or higher than a first threshold temperature.

  The operation of the present invention will be described below. As described above, the adsorption amount of the adsorbent decreases at a high temperature and increases at a low temperature, but the adsorption characteristics vary greatly depending on the adsorbent. Therefore, by selecting an appropriate adsorbent and controlling the temperature in the packed tower, it is possible to keep the composition variation on the downstream side of the packed tower within a desired range. FIG. 9 is a diagram conceptually showing the temperature dependence of the composition fluctuation suppressing performance of various adsorbents. Here, the “composition variation suppression performance” is an index indicating the ratio of the fluctuation range of the mixed gas having a composition variation at the inlet and the outlet of the packed tower, and the smaller the value, the higher the suppression performance. From the figure, the adsorbent A has a higher composition fluctuation suppressing performance than the adsorbent C in the normal environmental temperature range. However, the fluctuation suppressing performance decreases as the temperature increases, and is inferior to C at a certain temperature or higher. Further, compared with the adsorbent B, it is inferior to B at a temperature T1 or higher even in the normal environmental temperature range. In this case, by cooling the packed tower when the temperature in the packed tower reaches T1 or higher, high composition fluctuation suppressing performance can be maintained regardless of the environmental temperature.

In the present invention, the “mixed gas” is a concept including a raw material gas, a by-product gas, an exhaust gas, a generated gas by biomass, and the like in the chemical industry.
The said invention WHEREIN: The means which makes variable according to the composition fluctuation | variation width | variety in the downstream of the packed tower in which the 1st threshold temperature is desired can be further provided (Claim 2).
In the above invention, it is possible to further comprise means for stopping the cooling when the temperature in the packed tower is equal to or lower than the second threshold temperature (invention 3).
As the second threshold temperature, a temperature equal to or higher than the liquefaction temperature at the supply pressure of the component gas having the highest liquefaction temperature among the mixed gas components can be selected.
When a certain component falls below the liquefaction temperature, it causes an adverse effect such as stagnation of the liquid in the packed tower. Therefore, it is effective to provide a lower limit temperature according to the present invention.

  As the adsorbent used in the present invention, activated carbon activated carbon can be selected (claim 5). As will be described later, the activated carbon activated carbon has a high adsorption performance at room temperature or lower, but has a characteristic that the adsorption performance decreases at 40 ° C. or higher. According to the present invention, it is possible to prevent a decrease in adsorption performance, and it can be suitably used as an adsorbent.

In the above invention, fuel gas can be used as the “mixed gas” (Claim 6), and city gas mainly composed of methane can be used (Claim 7).
Currently, city gas nationwide is classified into 14 types of gas groups based on the Wobbe index and burning rate index, and city gas companies can supply city gas of the specified gas type to consumers in the supply area. As required by the Gas Business Law. For example, for 13A city gas mainly composed of CH4, it is determined that 52.7 ≦ WI ≦ 57.8 and 35 ≦ MCP ≦ 47. Here, the Wobbbe index (WI) is a numerical value obtained by dividing the calorific value H (MJ / m3) of the gas by the square root of the specific gravity s of the gas with respect to air.
WI = H / √s
This is an index of complete combustibility of gas equipment.
The combustion rate index (MCP) is expressed by the following equation.

上式において、Ｓi、ｆiはそれぞれ都市ガス中の各可燃性ガスの燃焼速度及び係数、Ａｉは都市ガス中の各可燃性ガスの含有率（体積百分率）、Ｋは減衰係数である。各係数の具体的数値についてはガス事業法に示されているため、ここでは省略する。
従って、本発明による吸着材充填塔通過後の混合ガスのＷＩ及びＭＣＰを、上記１３Ａ都市ガスの範囲に制御することにより、供給域内で都市ガス１３Ａ用機器を良好に燃焼させることができる。

In the above equation, Si and fi are the burning rate and coefficient of each combustible gas in the city gas, Ai is the content (volume percentage) of each combustible gas in the city gas, and K is the attenuation coefficient. Specific numerical values for each coefficient are shown in the Gas Business Law, and are therefore omitted here.
Therefore, by controlling the WI and MCP of the mixed gas after passing through the adsorbent packed tower according to the present invention within the range of the 13A city gas, the city gas 13A equipment can be burned well in the supply area.

  The invention according to claim 9 is filled with a supply line for supplying a mixed gas whose composition changes over time, and an adsorbent that is interposed in the supply line and has a characteristic that the composition fluctuation suppressing performance decreases with increasing temperature. In the mixed gas supply device equipped with the packed tower, the inside of the packed tower is cooled when the mixed gas temperature exceeds the first threshold temperature, and is cooled when the mixed gas temperature falls below the second threshold temperature. The composition variation adjusting method is characterized by stopping.

  A tenth aspect of the present invention provides a supply line that supplies fuel gas whose calorific value changes with time, and an adsorbent that is interposed in the supply line and has a characteristic that the performance of suppressing the calorific value variation decreases as the temperature rises. In a fuel gas calorific value adjusting device equipped with a packed tower, the packed tower is cooled when the temperature inside the packed tower becomes equal to or higher than the first threshold temperature, and becomes equal to or lower than the second threshold temperature. In this case, the heat generation amount adjustment method is characterized in that the cooling is stopped when the heat is discharged.

According to the present invention, it is possible to provide a mixed gas supply apparatus that enables gas supply while suppressing composition fluctuations within a certain range without being affected by environmental temperature.
Further, in the invention using fuel gas or city gas as a mixed gas, even if gas with a calorific value fluctuation is supplied from a supply source, the calorific value fluctuations over a wide range of practically assumed environmental temperatures. It is possible to supply the product to the customer while keeping the value within a certain range.

Hereinafter, embodiments of the present invention will be described in more detail with reference to FIGS. Needless to say, the scope of the present invention is described in the claims and is not limited to the following embodiments.
The present embodiment relates to a form in which the calorific value is adjusted using a fuel gas made from LNG as a “mixed gas”. LNG is mainly composed of methane (CH4), which is a light hydrocarbon, and includes propane (C2H6) and other heavy hydrocarbons (CmHn). In the following embodiments, “heat generation amount” means the total heat generation amount.

FIG. 1 is a diagram illustrating an overall configuration of a fuel gas supply apparatus 1 according to the present embodiment. The fuel gas supply device 1 includes, as main components, an LNG storage tank 4, a vaporizer 3, an adsorbent packed tower 2, and a cooling device 6 for cooling the adsorbent in the packed tower. These devices are connected by supply lines L1 to L3. A load device (for example, a gas engine) 5 is installed on the end side of the supply line L3. The LNG storage tank 4 stores LNG conveyed by a tank truck or the like. The adsorbent packed tower 2 is filled with an adsorbent 2a made of activated carbon coal.
The cooling device 6 is attached to the vaporizer 3 and receives a heat exchanger 6a that receives LNG cold heat, an adsorbent cooling heat exchange coil 6b in the packed tower 2, a circulation pump 6c, and a refrigerant that connects these devices. And a pipe 6e. The refrigerant pipe 6e is filled with antifreeze and is configured so that the antifreeze circulates between the devices. A flow rate adjusting valve 6d is disposed in the refrigerant pipe 6e. A temperature sensor S <b> 1 for measuring the adsorbent temperature is disposed in the packed tower 2.
The cooling device 6 further includes a control unit 7. In the control unit 7, a fluctuation range determination table shown in Table 1 and a heavy hydrocarbon (CmHn) liquefaction temperature determination table (not shown) created based on the steam table are stored. Based on these tables, the operation start / stop of the cooling device 6 is determined as described later. In addition, this fluctuation range determination table is determined from the measurement result (FIG. 6) of the fluctuation range under the condition of 2 ° C. to 80 ° C. in the coal raw material activated carbon described later.
In Table 1, the calorific value fluctuation range ΔH is an index indicated by ΔH = (Hmax−Hmin) / 2, that is, 1/2 of the difference between the calorific value maximum value Hmax and the minimum value Hmin.

  With the above configuration, the fuel gas supply device 1 vaporizes the LNG in the LNG storage tank 4 with the vaporizer 3 into natural gas, passes the packed tower 2 to adjust the calorific value fluctuation, and then passes through the supply line L3. Supply to the load device 5. The control unit 7 constantly monitors the measured value of the temperature sensor S1 during supply, performs start / stop of the circulation pump 6c and the opening / closing control of the flow rate control valve 6d based on the measured value, and arbitrarily sets the temperature in the packed tower. By controlling to the set temperature, the calorific value fluctuation of the natural gas at the outlet of the packed tower 2 is adjusted within a predetermined range.

  Next, a heat generation amount control flow in the fuel gas supply apparatus 1 will be described with reference to FIG. With the start of control, the operation start temperature T1 of the cooling device is first determined based on the fluctuation range determination table (S101). In order to keep the fluctuation range below 0.9 (MJ / m3). It is assumed that T1 is set to 40 ° C. During operation, the packed column temperature Ts is always measured by the temperature sensor S1 (S102), and it is determined whether Ts is equal to or higher than the threshold temperature T1 at a predetermined interval (S103). When Ts <T1, the process skips to step S106 described later. When Ts ≧ T1, it is next determined whether or not the cooling device 6 is already in operation (S104). When the operation is stopped, the cooling operation is started (S105). When the cooling device 6 is already in operation, the process skips to step S106.

  During the cooling operation, it is determined whether or not the measured value Ts of the temperature sensor S1 has reached the lower limit temperature T0 or less (S106). The lower limit temperature T0 is set to the normal pressure liquefaction temperature of n-butane, which is liquefied at the highest temperature among the fuel gas components, -0.5 ° C. When Ts ≦ T0, the component gas may be liquefied, so the operation of the cooling device is stopped (S107), the process returns to S102 and the above flow is repeated.

In addition, although the form which uses the normal pressure liquefaction temperature of n-butane was shown as cooling operation minimum temperature in this embodiment, it can also set to higher temperature. Thereby, the cooling operation time can be shortened, and the energy consumption required for cooling can be reduced.
In the present embodiment, an antifreeze liquid is used as the cooling refrigerant. However, other refrigerants such as chlorofluorocarbon, monohydric alcohol, glycol, LNG, LPG, CO2, ammonia, and the like may be used. Water can also be used when T0 exceeds 0 ° C.
In the present embodiment, the cold energy of the vaporizer is used. However, other cold heat sources can be used as the cold heat source.

In order to confirm the effect of the present invention, the adsorbent-filled container according to the present invention is set to various temperatures, a gas whose calorific value fluctuates periodically is flowed into the container, and the temperature dependence of the calorific value fluctuation is measured. did. The contents are described below (test adsorbent)
Coal raw material activated carbon was used as a test adsorbent. For comparison, a test using coconut shell raw material activated carbon was also conducted. Hereinafter, for the sake of simplicity, activated carbon A may be abbreviated as activated carbon A, and activated carbon B may be abbreviated as activated carbon B. The characteristics of the coal raw material activated carbon and coconut shell raw material activated carbon used in the test are shown in Table 2, and the pore size distribution (by nitrogen adsorption DFT method) is shown in FIG. FIG. 4 shows the pressure-adsorption / desorption characteristics of both activated carbons to methane and propane. The figure shows the amount of gas adsorbed on the activated carbon in the process of increasing the pressure from the vacuum state (0 KPa), and the gas is desorbed from the activated carbon in the process of decreasing the pressure after reaching the predetermined pressure. Shows the amount of adsorbed gas in this state.

(Test gas)
Flow LNG vapor (composition: CH4: 90.8%, C2H6: 5.0%, C3H8: 3.0%, i-C4H10: 0.6%, n-C4H10: 0.6%) for 2 minutes, then add to this gas for 1 minute By repeating the cycle of adding gas (propane 100%), a gas whose composition (calorific value) fluctuates periodically was prepared. The test gas had a calorific value variation of a minimum of 44.8 MJ / m3 and a maximum of 50.5 MJ / m3, and a calorific value variation range ΔH = 2.85 MJ / m3.
Here, ΔH is an index indicated by ΔH = (Hmax−Hmin) / 2, that is, 1/2 of the difference between the maximum calorific value Hmax and the minimum value Hmin.

(Test equipment)
Filling container (30 cc internal capacity) with adsorbent and maintaining the ambient temperature at 2 ° C, 25 ° C, 40 ° C, 60 ° C and 80 ° C, the test gas with the above composition is superficial The calorific value of the gas flowing out from the container at 2000 h ⁻¹ and flowing out of the container was measured with a calorimeter (Advantica, product name: GasPT).

(Measurement result)
In FIG. 5, the calorific value fluctuation | variation measurement result of the coal raw material activated carbon in each temperature is shown. In the same figure, the measurement results under conditions where the filled container is not passed are also shown for reference. FIG. 6 is a diagram showing the temperature dependence of the heat generation amount fluctuation range ΔH. From the figure, it can be seen that the value of ΔH increases as the temperature of the coal activated carbon increases.

(Comparative example)
FIGS. 7 and 8 are graphs showing temporal changes in calorific value fluctuations of coconut shell raw material activated carbon, which is a comparative example, and temperature dependence of ΔH, respectively. As is clear from the comparison between FIG. 6 and FIG. 8, the coal raw material activated carbon has a higher calorific value suppression effect under conditions of room temperature or lower. However, it is reversed when the temperature is higher than 40 ° C. From this, by cooling the filling container so that the environmental temperature does not become 40 ° C. or higher using the coal raw material activated carbon, it is possible to always maintain a high calorific value suppression effect as compared with the case using the coconut shell raw material activated carbon. Become.

  The present invention is not limited to suppressing fluctuations in the calorific value of the fuel gas, but also suppresses fluctuations in the composition of a mixed gas composed of a plurality of gas components that vary in composition, such as raw material gas, by-product gas, exhaust gas, and produced gas from biomass. It can be widely used for applications.

It is a figure which shows the structure of the fuel gas supply apparatus 1 which concerns on one Embodiment of this invention. It is a figure which shows the calorific value fluctuation | variation suppression control flow of the fuel gas supply apparatus. It is a figure which shows the pore diameter distribution of the coal raw material activated carbon which is a test adsorption material, and the coconut husk raw material activated carbon which is a comparative adsorption material. It is a figure which shows the adsorption | suction characteristic with respect to methane and propane of coal raw material activated carbon and coconut husk raw material activated carbon. It is a figure which shows the time course of the calorific value fluctuation | variation of coal raw material activated carbon. It is a figure which shows the temperature dependence of the emitted-heat amount fluctuation | variation of coal raw material activated carbon. It is a figure which shows the time course of the calorific value fluctuation | variation of the coconut shell raw material activated carbon. It is a figure which shows the temperature dependence of the emitted-heat amount fluctuation | variation of coconut shell raw material activated carbon. It is a figure which illustrates notionally the operation of the present invention. It is a figure which shows the structure of the conventional fuel gas supply apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel gas supply device 2 ... Adsorbent packed tower 2a ... Adsorbent 3 ... Vaporizer 4 ... LNG storage tank 5 ... Load device 6 ... Cooling device 7... Controllers L1 to L3... Supply line S1.

Claims (10)

A supply line for supplying a mixed gas whose composition changes over time;
A packed tower filled with an adsorbent having a property of intervening in the supply line and decreasing in composition fluctuation suppression performance as the temperature rises;
When the packed tower temperature is equal to or higher than the first threshold temperature, means for cooling the packed tower,
A mixed gas supply apparatus comprising: The mixed gas supply apparatus according to claim 1, further comprising means for varying the first threshold temperature in accordance with a desired composition fluctuation range on the downstream side of the packed tower. The mixed gas supply apparatus according to claim 1 or 2, further comprising means for stopping cooling when the temperature in the packed tower is equal to or lower than the second threshold temperature. The fuel gas supply apparatus according to claim 3, wherein the second threshold temperature is equal to or higher than a liquefaction temperature at a supply pressure of a component gas having the highest liquefaction temperature among the mixed gas components. The mixed gas supply device according to claim 1, wherein the adsorbent is activated carbon activated carbon. 6. The mixed gas supply apparatus according to claim 1, wherein the mixed gas is a fuel gas. The mixed gas supply device according to claim 6, wherein the fuel gas is a city gas containing methane as a main component. Using the mixed gas supply device according to claim 6 or 7,
A fuel gas heat generation amount adjustment device configured to adjust a fuel gas heat generation amount fluctuation adjustment. A supply line for supplying a mixed gas whose composition changes over time;
In a mixed gas supply apparatus comprising: a packed tower that is interposed in a supply line and packed with an adsorbent having a characteristic that the composition fluctuation suppression performance decreases as the temperature rises.
When the packed tower temperature is equal to or higher than the first threshold temperature, the packed tower is cooled, and when the temperature is equal to or lower than the second threshold temperature, the cooling is stopped.
A method for adjusting composition fluctuations. A supply line for supplying fuel gas whose calorific value changes over time;
In a calorific value adjustment device comprising: a packed tower filled with an adsorbent that intervenes in the supply line and has a characteristic that the calorific value fluctuation suppression performance decreases as the temperature rises.
When the packed tower temperature is equal to or higher than the first threshold temperature, the packed tower is cooled, and when the temperature is equal to or lower than the second threshold temperature, the cooling is stopped.
The calorific value adjustment method characterized by this.

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