CN101705113B - Entrained flow gasifier water-cooling circulating system with ejector - Google Patents

Abstract

A water-cooling circulation system for an entrained entrained bed gasifier with an ejector. The system is based on a traditional entrained-bed water-cooling circulation system, and an ejector is added below the steam-water separator; The outflow steam is condensed into low-temperature water, and this part of low-temperature water is pumped into the primary fluid inlet of the ejector by means of a circulation pump, while the saturated water in the steam-water separator flows directly into the secondary fluid inlet of the ejector through the pipeline. In this way, the mixed working fluid at the outlet of the ejector will have a larger flow head, which can increase the mass flow rate of the downcomer and the entire water cooling circulation system, ensuring the system safety of the water cooling heat transfer of the gasifier. Therefore, the present invention can not only avoid flow instability and heat transfer deterioration in natural circulation, but also make full use of the gravity pressure drop difference in the water cooling cycle to partially compensate for the resistance loss along the flow of the working fluid. For forced circulation, the power consumption of the circulation pump can be reduced.

Description

A water-cooling circulation system for an entrained-flow gasifier with an ejector

technical field

The invention relates to a water-cooling circulation system of a water-cooled entrained-bed gasification furnace, which belongs to coal gasification combustion equipment.

Background technique

Coal gasification technology is the core technology for clean and efficient conversion of coal, while entrained bed gasification represents the development direction of coal gasification technology. The entrained bed gasification furnace mostly adopts pure oxygen high-pressure gasification to reduce the volume of the gasification furnace and maintain the high temperature condition in the furnace. The gasification temperature (outlet) of the entrained bed gasification furnace is usually between 1350 and 1600°C, and the maximum temperature in the furnace is as high as 2000°C. Obviously, such a high temperature environment has very high requirements on the temperature resistance of the furnace body.

One approach is to use a refractory-lined gasifier structure with pressure tanks. Refractory linings have strict requirements on materials, usually expensive high-Cr bricks, which need regular maintenance and replacement, and can operate for a long time under high-temperature reducing conditions. But even if high Cr bricks are used, the ablation is still fast after the temperature exceeds a certain level, so it is usually limited to below 1500 °C. At the same time, in order to maintain a stable reaction and facilitate the removal of ash in coal, liquid slagging is generally used. Therefore, the requirements for the ash melting point of gasified coal are relatively strict, usually below 1300 °C. Therefore, the applicable range of coal types of the adiabatic gasifier with refractory lining is relatively small. In order to improve the adaptability of coal types and use coal with high ash melting point, it is necessary to maintain the gasifier at a higher temperature. At this time, the life of the refractory lining will not be enough to ensure the economical efficiency of the equipment. Another method is the water-cooled wall gasifier. When the vertical tube screen membrane water wall or coil membrane water wall technology is used, the slag layer hanging on the water wall can be used to protect the water wall, so that the gasification device can be used for a long time. cycle. From this point of view, water wall technology is superior to refractory brick technology, and it will be the main direction of gasifier development in the future.

In the water wall gasifier, the design of the water cooling cycle can be divided into two categories, namely natural circulation and forced circulation. The natural circulation method makes full use of the working medium density difference between the descending section and the ascending section of the pipeline. Its advantage is economical, but the flow rate of the working medium cannot be guaranteed, so there are hidden dangers in terms of heat transfer safety. The forced circulation method introduces a circulation pump to ensure the heat transfer safety of the water cooling cycle, but at the same time its economy is reduced.

Contents of the invention

In view of the deficiencies of the two water-cooling circulation methods in the current water-walled gasifier, the purpose of the present invention is to provide a water-cooling circulation system for the gasifier with an ejector, so that it can not only make full use of the pipeline between the descending section and the ascending section. The working fluid density difference between them, and at the same time ensure the mass flow rate of the working fluid by setting the ejector.

Technical scheme of the present invention is as follows:

A water-cooled circulation system for an entrained-flow gasifier with an ejector, the system includes a steam-water separator, a water-cooled wall, a water-cooled wall inlet header, a downcomer, a water-cooled wall outlet header and a condenser, characterized in that: The system also includes an ejector and a circulation pump; the steam-water separator is connected to the condenser through a saturated steam outlet pipe; the condenser is connected to the primary fluid inlet of the circulation pump and the ejector in sequence through a pipeline; the steam-water separator The outlet of the ejector is connected with the secondary fluid inlet of the ejector through the saturated water outlet pipe; the outlet of the ejector is connected with the inlet header of the water cooling wall through the downcomer; the outlet header of the water cooling wall is connected with the steam-water separator through a pipe.

The ejector of the present invention adopts the ejector II type.

The invention takes into account the high gasification temperature in the entrained bed gasification furnace and the strict requirements on the temperature resistance of the furnace body, makes full use of the working medium density difference between the downcomer and the ascender in the water cooling cycle, and introduces an ejector To achieve the mixing of two working fluids with different pressure heads and temperatures, to ensure the mass flow rate of the working fluid in the water wall, thereby ensuring the effectiveness and safety of the water wall, and avoiding the slowdown or even stagnation of the flow of the working fluid The water-cooled wall tube explosion and shutdown caused by the water wall gasifier are of great significance to the long-term stable operation of the entrained bed gasifier.

Description of drawings

Fig. 1 is a schematic structural diagram of a water-cooled circulation system for a water-cooled gasifier provided by the present invention.

In the figure: 1-saturated steam outlet pipe; 2-condenser; 3-circulation pump; 4-ejector; 5-saturated water outlet pipe; 6-downcomer; 7-water wall inlet header; 8-water wall ; 9-Water wall outlet header; 10-Steam water separator.

Detailed ways

The specific structure, working principle and working process of the present invention will be further described below in conjunction with the accompanying drawings.

The present invention provides a gasifier water-cooled circulation system with an ejector, the system includes a steam-water separator 10, a water-cooled wall 8, a water-cooled wall inlet header 7, a downcomer 6, a water-cooled wall outlet header 9, a condensing 2, ejector 4 and circulation pump 3; the steam-water separator 10 is connected to the condenser 2 through the saturated steam outlet pipe 1; The inlet is connected; the steam-water separator 10 is connected with the secondary fluid inlet of the ejector 4 through the saturated water outlet pipe 5; the outlet of the ejector 4 is connected with the water wall inlet header 7 through the downcomer 6; the water cooling The wall outlet header 9 is connected to the steam-water separator 10 through a pipeline.

Principle of the present invention is:

The temperature inside the entrained-bed gasifier is higher than that of the fixed-bed and fluidized-bed gasifiers, so the requirement for the cooling capacity of the water-cooled wall is also higher. In the water cooling cycle including the water wall, steam-water separator, etc., the temperature of the working medium in the descending pipe section is low, and it is single-phase water, so the gravity pressure drop is large, while the temperature of the working medium in the ascending pipe section is high, and most of the pipe sections are It is a two-phase flow of soda and water, so the pressure drop at gravity is small. The gravity pressure drop difference between the descending pipe section and the ascending pipe section can provide power for the flow of working fluid in the entire circulation loop. At the same time, the circulation pump is used to increase the pressure head of a part of the cooling water, which is transformed into an increase in the pressure head of the working fluid in the entire downcomer section through the mixing of the ejector, so that the pressure head of the working fluid in the water cooling cycle can be further increased. The mass flow rate ensures the safe and reliable flow and heat transfer of the water wall.

Working process of the present invention is:

The steam-water separator 10 is connected to the outlet header 9 of the water-cooled wall through pipes, separates steam and saturated water, and sends the steam to the condenser 2 for condensation. The water condensed by the condenser 2 is connected to the circulation pump 3 through the pipeline to realize pressurization, and enters the primary fluid inlet of the ejector 4 through the pipeline, and the saturated water separated by the steam-water separator 10 passes through the saturated water outlet pipeline 5 and The secondary fluid inlet of the ejector 4 is connected; the secondary fluid is ejected by the primary fluid, which increases the flow head, so the mass flow rate of the working medium in the downcomer 6 and the water cooling wall 8 is increased, and the water cooling The cooling effect of the working medium in the wall is also enhanced. The working fluid absorbs heat in the water-cooled wall 8 and then passes through the outlet header 9 of the water-cooled wall, and finally returns to the steam-water separator 10 .

Example:

The working pressure of the working fluid in the water wall is 5MPa. The temperature of the saturated water coming out of the steam-water separator 10 is about 264° C., and enters the secondary fluid inlet of the ejector 4 through a pipeline. The saturated steam coming out of the steam-water separator 10 has a temperature of about 264°C, enters the condenser 2 through a pipeline for condensation, and becomes unsaturated water of about 105°C, then enters the circulation pump 3 to increase the pressure head, and enters through the pipeline Primary fluid inlet for ejector 4. After mixing in the ejector, the working fluid becomes unsaturated water at about 188°C. Thereafter, the working fluid enters the water-cooled wall inlet header 7 through the downcomer section 6, and then passes upward through the water-cooled wall 8 to be heated, becomes a steam-water two-phase flow, enters the water-cooled wall outlet header 9, and returns to the steam-water separator 10 through the pipeline. The length of the downcomer section is 6m, and the working fluid density in it is 881kg/m ³ , so the gravity pressure drop of the downcomer section is 51.9kPa; Saturation heating to saturated state, the average density of the working fluid in this section is 835kg/m ³ , and the gravity pressure drop is 14.9kPa; The density is 0.0098, the average cross-sectional vapor content is 0.1324, the average density of the two-phase flow is 678kg/m ³ , and the gravity pressure drop is 27.8kPa; thus, the gravity pressure difference is 9.2kPa. The pressure head of the working medium provided by the circulating pump and ejector is 4.4kPa. The total pressure head in the circulation loop is then 13.6 kPa. The viscosity of the working fluid in the downcomer section is 1.64×10 ^-7 m ² /s, and the average viscosity of the working fluid in this section when the water wall is heated from the inlet header to the saturation of the working fluid is 1.27×10 ^-7 m ² /s, The full liquid phase friction coefficient of the working fluid between the saturated water wall and the outlet header is 0.059566. From this, it can be calculated that the mass flow rate of the working fluid in the water cooling cycle is about 1200kg/m ³ s.

If the natural circulation method is used, the mass flow rate of the working fluid in the water cooling cycle will only be 800kg/m ³ s when the height of the water cooling wall is the same. It can be seen that the water cooling safety of the present invention is better than natural circulation.

And if the mode of forced circulation is used to realize the same working medium mass flow rate of the present invention, the power of the circulating pump consumed will be more than about 3 times of the present invention. Therefore, in terms of economy, the forced circulation mode is inferior to the present invention .

Claims (1)

1. airflow bed gasification furnace water-cooling circulating system with injector; This system comprises steam separator (10); Water wall (8), water wall inlet collection case (7), downtake (6); Water wall outlet collection case (9) and condensing surface (2), it is characterized in that: said system also comprises injector (4) and recycle pump (3); Described steam separator (10) links to each other with condensing surface (2) through saturation steam outlet conduit (1); Condensing surface (2) links to each other with a fluid intake of recycle pump (3) and injector (4) through pipeline in order; Described steam separator (10) links to each other through the secondary fluid inlet of saturation water outlet conduit (5) and injector (4); Described injector (4) outlet links to each other with water wall inlet collection case (7) through downtake (6); Water wall outlet collection case (9) links to each other with steam separator (10) through pipeline.

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