JPH021081B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process of gasifying a hydrocarbon raw material consisting of coal, heavy oil, or a mixture thereof and converting it into clean fuel gas or raw material gas for chemical industries, particularly in a gasification furnace. This invention relates to a method for cooling generated high-temperature crude gas and recovering heat.

Coal, heavy oil, etc. can be converted into chemical industrial raw material gas or clean fuel gas by heat treatment.
Each of the above gases is not obtained only through a heat treatment process (gasification process), but is produced through a comprehensive process consisting of a purification process, other processes, and a gas transportation line that connects each process. This comprehensive process takes various forms depending on the type of product gas being produced.
In either case, a gasification step and a purification step are always required. The gasification process is a sector in which raw materials such as coal are converted into gas at high temperatures using steam or gasifying agents. The gases generated here are called crude gases, and include inorganic gases such as hydrogen and carbon monoxide, organic gases that are compounds of carbon and hydrogen, high-boiling distillate gases collectively known as tar, and polycondensates of these gases. It is a mixed gas such as The purification process removes unnecessary substances from this mixed gas, and is usually connected to the gasification process by a gas transport line, into which high-temperature gas is introduced.
Since high temperature purification is not possible in this process with existing technology, in most cases the crude gas is cooled and purified at low temperature.

The problem here is that some of the tar generated during the gasification process condenses and becomes droplets as it cools.
The problem is that it adheres to or sticks to the internal walls of the gas transportation line and the equipment that follows it, eventually resulting in the shutdown of the system. Many inventions have been made to solve this serious problem. These inventions can be divided into those that reduce tar condensation and adhesion by selecting operating conditions (temperature and gas flow rate), and those that forcibly remove the adhesion. The former method can reduce the amount of adhesion and reduce problems, but it is difficult to select operating conditions and cannot be effective unless the conditions are maintained at all times. Sometimes performance decreases dramatically. On the other hand, the latter is useful for troubleshooting as it forcibly removes the deposits using solid particles, etc. However, since it removes with a large amount of solid particles, it requires a separation device to separate and remove the solid particles. There are drawbacks. Further, all of these methods have the disadvantage that they do not reach the point of recovering the sensible heat of the high-temperature crude gas and have a low heat gain rate.

In contrast to the above method, a method has been proposed in which the sensible heat of high-temperature crude gas is recovered while preventing troubles caused by tar (Japanese Unexamined Patent Publication No. 52-5805). This invention cools high-temperature crude gas using a fluidized bed under specific conditions to recover high-quality heat and steam. In principle, this prevents blockage problems by attaching tar to the particles in the fluidized bed and separating it from the crude gas, while also optimizing heat recovery using heat transfer tubes inserted into the fluidized bed. The operating conditions for this are limited. This method has the advantage of being able to recover heat, but because it uses a fluidized bed, tar cannot be completely removed, and some of the tar can enter subsequent equipment and cause blockage problems.

The present invention has been made to improve the above-mentioned drawbacks, and its purpose is to provide a method for cooling and recovering heat from high-temperature crude gas, which prevents clogging problems caused by tar.

That is, the feature of the present invention is that, in cooling high-temperature crude gas generated from a heat treatment process using hydrocarbons as a raw material, the high-temperature crude gas is cooled with an indirect cooler made of a fluidized bed, and the sensible heat of this high-temperature crude gas is absorbed. The high-temperature crude gas is collected and then cooled in a direct cooler having a ventilate section. A heat transfer tube is provided to allow gas to flow in and to pass a cooling medium through the upper fluidized bed section, and the temperature of the lower fluidized bed is controlled to be higher than the temperature of the upper fluidized bed.

The present invention will be explained in detail below with reference to the drawings. The indirect cooler 1 is connected to a direct cooler 3 downstream thereof by a gas transport line 2, and fluidized particles 4, heat transfer tubes 5, and a screen 6 are inserted therein.
High temperature crude gas generated in the gasification process (not shown) 8
is introduced from the lower part of the indirect cooler 1 and causes the fluidized particles 4 in the indirect cooler 1 to flow. fluid particle 4
When moving vertically and horizontally within the indirect cooler 1, it comes into contact with the heat exchanger tube 5, which is an insert, and is cooled. The cooled fluidized particles 4 descend in the indirect cooler 1 and come into contact with the crude gas, causing high boiling point tar in the gas to condense and adhere to the surface of the particles, and at the same time receive the sensible heat of the gas and heat the particles. Thermal decomposition of tar attached to the surface,
solidify. The solidified particles adhere to the particles rise again, contact the heat exchanger tube 5, and are cooled. That is, the fluidized particles 4 repeatedly cool, heat, condense, adhere, and solidify high-boiling point tar while moving within the indirect cooler 1 and capture tar in the crude gas. On the other hand, the heat transfer tube 5 indirectly carries out the heat given from the fluidized particles 4 to the outside of the indirect cooler 1 by flowing cold water or the like inside the tube, thereby providing a necessary heat source for the gasification furnace or the like. In addition, the screen 6 controls the amount of fluidized particles 4 moving inside the indirect cooler 1, and the amount of particles moving up and down increases or decreases depending on the aperture ratio of the screen 6. As a result, the screen 6
Provides a temperature difference between the upper and lower zones. That is, high-temperature crude gas of 700°C to 950°C generated during coal gasification is introduced into the indirect cooler 1, and the temperature is 400°C to 550°C, preferably about 450°C at the bottom of the screen 6, and about 450°C at the top of the screen 6. A screen 6 is installed that can obtain a temperature difference of 350°C to 450°C, preferably 50°C to 100°C lower than the lower temperature, and the high boiling point tar contained in the crude gas is collected in two stages. The efficiency is increased and the collected tar is coked in the lower zone. Approximately 90 to 95% of the tar that has a boiling point above this temperature can be collected in the indirect cooler 1, but since it is a fluidized bed (high temperature crude gas bubbles rise in the indirect cooler 1, a small amount of tar A few percent (free pass) is discharged from the indirect cooler 1. This discharged tar adheres to the inner wall of the gas transport line 2, but its amount has decreased significantly and is blasted by a small amount of fluid particles scattered from the indirect cooler 1. Caulking problems rarely occur. The temperature of the gas passing through the gas transport line 2 is usually equal to or slightly higher than the temperature of the outlet gas in the indirect cooler 1 (10°C to 30°C).
℃), and these gases are directly introduced into the cooler 3. In order to increase the flow velocity of these gases, the direct cooler 3 consists of a gradual contraction section, a thin tube for high-speed flow, and a direct coolant jetting section at the high-speed flow section, and directly quenches the gas. As a result, tar and low boiling point distillate tar that have passed through the indirect cooler 1 are instantly cooled down to a temperature at which the tar is no longer thermally decomposed, and the tar adhering to the tube wall is caused to flow down at a high speed. That is, the tar is kept in a liquid state and sent to the subsequent process without being solidified.

Example 1 70wt% Iranian heavy vacuum residual oil as raw material,
Using a mixed slurry of 30wt% Pacific coal (0.1-0.42mm). The high-temperature crude gas gasified at 850℃ using oxygen and water vapor as gasifying agents is heated to an inner diameter of 250mm, a height of 2m,
It was introduced into an indirect cooler that had a heat transfer tube and a screen inside and was filled with 63 kg of silica sand with an average diameter of 260 μm as fluidized particles (the temperature inside the container was 490°C at the bottom of the screen,
Cooling water was supplied into the heat transfer tube so that the temperature at the top was 450°C.) The gas leaving the indirect cooler was sent directly to the cooler via a gas transport line with an inner diameter of 42 mm. direct cooler
It has a narrow tube with an inner diameter of 12.7 mm with a tightened part that is constricted at a 17° angle, and a coolant spout that opens in the narrow tube. In this section, water was used as a coolant to rapidly cool the gas introduced at 430°C to 210°C. Continuous operation was carried out under these conditions for 22 hours, and the status of tube blockage due to coking during operation was investigated using a differential pressure measuring device connected to the indirect cooler inlet and direct cooler outlet. As a result, there was no rise in differential pressure, no blockage in the pipes due to coking was observed, and the indirect cooler pumped water vapor at 230°C at 20°C per hour.
Obtained in Kg. After the experiment, we dismantled each part and observed the inside, but found that the caulking was intact and there were no problems with the subsequent water-cleaning scrubber section.

Comparative Example 1 The direct cooler in the example was removed, the gas transport line was directly connected to the succeeding scrubber, and continuous operation was performed for 22 hours under the same conditions as in the example. The results showed that the inner wall of the gas transport line pipe at the inlet of the scrubber was There was caulking with a thickness of 15 to 18 mm, and the gas flow path was on the verge of being blocked. There was also caulking of about 2 to 4 mm on the inlet side of the scrubber.

Comparative Example 2 The indirect cooler in the example was removed, the transport line was directly connected to the gasifier, and continuous operation was performed for 100 hours under the same conditions as in the example. During operation, the differential pressure in the gas transportation line gradually increased, reaching about 100 times the differential pressure at the beginning of operation in about 20 hours. Therefore, caulking was removed four times during operation using a manual pipe scraper. In other words, continuous operation was impossible without a scraper.
In addition, when we dismantled and inspected the line after operation, we found that there was caulking of about 15 to 20 mm on the inner wall of the gas transportation line.

According to the present invention, heat can be recovered while preventing coking troubles, so that the heat gain rate of the process can be improved.

[Brief explanation of drawings]

The drawings are schematic diagrams showing the overall configuration of the present invention. 1...Indirect cooler, 2...Gas transportation line, 3
... Direct cooler, 4 ... Fluid particles, 5 ... Heat exchanger tube, 7 ... Coolant, 8 ... High temperature crude gas.

Claims (1)

[Claims] 1. The high-temperature crude gas generated in the heat treatment process for gasifying hydrocarbon raw materials is cooled by passing it through an indirect cooler consisting of a fluidized bed having fluidized particles, and the sensible heat of this high-temperature crude gas is recovered, and then the ventilate section Pass this hot crude gas through a direct cooler with
A method of supplying a refrigerant from the outer periphery of the ventilate part and bringing it into contact with the crude gas for cooling, wherein the fluidized bed is formed into two upper and lower layers by a perforated plate, and the high-temperature crude gas is introduced from the lower fluidized bed side. . A method for cooling and recovering heat from high-temperature crude gas, characterized in that a heat transfer tube for passing a cooling medium is provided in an upper fluidized bed section, and the temperature of the lower fluidized bed is controlled to be higher than the temperature of the upper fluidized bed.