JPH0140874B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to the cooling of produced gas in a coal gasification plant, and is concerned with improving the cooling efficiency by reducing tar condensation and scraping recovered tar, and improving the cooling efficiency in the process of this plant. This invention relates to the structure of a coal cracked gas cooling device for final dust removal.

<Prior Art> There are two methods for cooling gas: ordinary tube heat exchange through indirect contact of refrigerant, and direct injection of refrigerant.

As a conventional gas cooling device of this type, there is a device disclosed in Japanese Patent Publication No. 48121/1983 as shown in FIG.

This device cools coke oven gas.
The introduced gas is at a low temperature of approximately 80 to 85 degrees Celsius, and tar is first collected from the gas flow that contacts the outer surface of the tube group 4 through which the cooling liquid of 50 to 60 degrees Celsius passes through the indirect cooler. The gas is sent to an unfilled column 6. This tower is equipped with three sprays, which spray a mixture of the tar-containing liquid stored at the bottom of the unfilled tower and the collected liquid from the tubular cooling tower, and exchange it with the gas. The sensible latent heat is collected and cooled.

That is, it is characterized by having an unpacked column that separates tar and other components from coke oven gas at a low temperature of 80 to 85°C through self-flow contact with the sprayed droplets.

<Problems to be Solved by the Invention> The present invention is characterized in that coal decomposition gas has a temperature of about 1000°C and the generated gas contains a considerable amount of tar, and if the temperature of the refrigerant is extremely low, the tar in the gas will be removed. It condenses and adheres to the surface of heat transfer tubes and solidifies, impeding not only heat transfer performance but also gas flow function.

Therefore, by setting and controlling the temperature of the tube wall so that even if tar adheres to the tube, it does not impede heat transfer or flow, and by designing a heat exchanger that allows condensed tar to separate under natural flow, the final result is It is necessary to propose a system and structure for dust removal and tar mist collection.

The nature of tar in gas is that it condenses and solidifies at about 150°C, and when it adheres to pipe walls, it inhibits heat transfer and makes recovery of the tar difficult. For this purpose, it is necessary to set the tube wall temperature to around 200°C and to create a structure that allows for good discharge of tar.

Furthermore, a device is required to thoroughly remove tar that cannot be removed even with this method.

Since high-temperature dust removal using a fluidized bed of small aluminum balls has become possible, the temperature of the gas supplied to the cooling device, which is the object of the present invention, is 400 to 500°C. (Japanese Unexamined Patent Publication No. 1982-8296, filed on the same day as the present invention, shows a piping diagram of a coal cracking gas treatment plant, and shows the arrangement of the cooling device and processing conditions of the present invention.) Object of the present invention There is also a demand for suitable tar removal and heat recovery for gases at temperatures of 400 to 500°C.

<Purpose of the Invention> The present invention provides a gas cooling device that appropriately removes tar from gas at a high temperature of about 500°C among equipment constituting a coal cracking gas plant and obtains a product gas, and performs heat recovery. The purpose is to make it suitable.

<Summary of Means> In summary, the present invention is an apparatus for cooling high-temperature coal decomposition gas containing fine sticky droplets such as dust and tar to obtain generated gas, in which a gas inlet channel and a scraper are connected by a plurality of vertical straight pipes. A gas cooler, a gas-liquid separator, a circulation pump, a low-pressure boiler for heat recovery, and an oil injection nozzle for the scrubber are arranged in series to cool the gas passing through the straight pipe section and generate steam. Generated pressure 15Kg/cm ²
This paper proposes a coal cracked gas cooling system consisting of the above-mentioned high-pressure side boiler.

<Example> FIG. 1 shows a system flow for explaining the structure and function of a cooling device according to an example of the present invention.

A gas 1 containing tar and dust enters a cooler 2. The cooler 2 is vertical, and includes a plurality of vertical heat exchanger tubes 3, rising tubes 5, downcomer tubes 6, boiler drums 4, water supply tubes 8, and steam piping 7, each having a tube diameter of 75 to 100 mm to form a waste heat boiler. . Tar condenses inside the heat transfer tube and forms a film of condensed droplets on the inner surface of the tube.
According to experimental findings, it has fluidity at temperatures above 150°C and flows down the wall of the heat transfer tube under its own weight.
Therefore, the pressure of the can water as a waste heat boiler can be set to a sufficient temperature (saturation temperature) to ensure the fluidity of tar. For example, if the weight is 15 kg/cm ² g, the entire area of the heat exchanger tube can be maintained at 200° C. or higher.

The tar and gas flowing down the heat transfer tube are further cooled by direct injection of recovered tar through a nozzle 10 at the scrubber 9, which has an oil scrubber function on the outlet channel, and at the same time has the effect of cleaning tar mist and dust. List. In this scrubber, a cylindrical part with a larger diameter than the main body of the cooler 2 and an inverted conical part are connected to form the outlet gas channel (passage part) main body, and the axis of the multiple oil (tar) injection nozzles 26 is centered The scrubber has a so-called radial shape on the peripheral wall that is oriented toward the axis of the scrubber body, and the gas exiting the heat transfer tube is sufficiently cleaned and cooled.

Since this oil injection nozzle 26 sprays a tar-containing liquid of 5 to 10 kg/cm ² , it becomes a fine mist and collides with the tar liquid flowing down from the heat transfer tube 3 to atomize it and to reduce the diameter of the scrubber body. Since the diameter of the gas is much larger than the diameter of the heat transfer tube, the flow rate of the gas decreases at this point, so that the spray and mixing are even better, resulting in a slubbing effect.

Next, liquid gas coexistence material (mixture) (temperature is 200℃)
The gas passes through a conduit 11 to a gas-liquid separator 12, such as a cyclone separator, and the gas is exhausted from a pipe 13 as the final product gas, and the separated liquid (tar) is pressurized by a pump 14 to a low pressure of 200°C at the inlet and 150°C at the outlet. The boiler recovers the heat and cools it to some extent, and the heat is recycled through the pipe 16 to the scrubber nozzle 10. The surplus is discharged through the pipe line 17.
Based on the above temperature conditions, this low pressure boiler has a pressure of 3
It becomes a boiler of about Kg/cm ² .

FIG. 2 shows the structure of the cooler of the present invention, and FIG. 3 shows details of the tube plate connection at the upper part of the heat exchanger tube.

The gas at 400 to 500° C. enters the channel 19 from the nozzle 18, further flows down the heat transfer tube 20, and reaches the scrubber 22 via the lower tube plate 21. channel 1
9 (chamber-like passage) has an inner surface kept warm by a heat insulating lining 23, and the tube sheet is protected by fixing a ferrule 25 between the lining and a shroud plate 24. The heat transfer tube 20 is characterized by using a relatively large diameter tube having an inner diameter of, for example, 75φ to 100φ (mm) and by being installed vertically, so that even if tar etc. condenses and forms droplets, the gas flow resistance is reduced. It has a structure in which it flows downward without increasing. If possible, it is desirable to reduce the number of heat exchanger tubes so that even gas distribution to the heat exchanger tubes in the inlet channel is possible even in large-capacity plants. Several units can be used in parallel to increase capacity, which is one of the major effects of this invention.

<Effects> By implementing this invention, the following effects can be obtained.

(1) It is possible to cool high-temperature dust- and tar-containing gas without the problem of tar condensation, and heat exchange type waste heat recovery (recovery by steam generation in the high-pressure side boiler and low-pressure boiler) is also possible. improve the thermal economy of

The temperature of the gas flowing into the heat transfer tube is 400 to 500℃, so the tube wall in this heat transfer tube section is set to 200℃, the boiler pressure is set to 15Kg/ ^cm2 to prevent tar solidification, and the tube wall temperature is set to 200℃. can do.

The obtained steam can be used for internal purposes, low pressure turbines, etc.

(2) By using the recovered tar-containing liquid in the scrubber, there is no need to introduce another refrigerant, and cooling, dust removal, and tar removal are possible, making it possible to effectively utilize tar that would otherwise be a hindrance to utility plants. Ta.

Scrubber and gas-liquid separator 1 connected to it
2 is used in combination, the tar content, which was about 3% of the coal processing amount at the outlet of the coal gasifier, is reduced to about 0.2% by adopting a high-temperature dust removal device (fluidized bed type). The load on the cracked gas cooling system has also been reduced. In addition to these, by using the cooling device of this application, the tar component in the generated gas is 0.7
g/ ^Nm3 .

[Brief explanation of drawings]

Fig. 1 is a drawing showing the arrangement and piping system of the device according to the present invention, Fig. 2 is a longitudinal sectional view of the gas cooler,
FIG. 3 is a partial cross-sectional view showing details of the connection between the heat transfer tubes and the upper tube sheet, and FIG. 4 is a piping diagram of a conventional coke oven gas cooling device, which is a gas cooling device. 1... Gas containing dust, 2... Gas cooler,
3, 20... Heat exchanger tube, 19... Channel, 22... Scrubber.

Claims (1)

[Claims] 1. In an apparatus for cooling high-temperature coal decomposition gas containing fine sticky droplets such as dust and tar to obtain generated gas, a gas inlet channel and a scrubber are connected by a plurality of vertical straight pipes. A cooler, a gas-liquid separator, a circulation pump, a low-pressure boiler for heat recovery, and an oil injection nozzle for the scrubber are arranged in series to cool the gas passing through the straight pipe section and generate steam. A coal cracking gas cooling device characterized by being equipped with a high-pressure side boiler with a pressure of 15 kg/cm ² or more. 2. The coal cracked gas cooling device according to claim 1, wherein the steam pressure of the low pressure boiler is 3 kg/cm ² g or more.