JPS58167685A - Coal gasification - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the sulfurization of coal, and particularly to the sulfurization of coal.
shGas-Lurgl slaglng gasl
fler) and the recycling of tar and other liquid by-products so that they are gasified.

Lurgl dry-b
ottom gaslfler) and pritish
Gas-Lurglslaglng gaslfla
r) is well known in coal gasification technology. For example, John Willey and Sons
The Chemistry Oh! is published by Wllay & 5ons Inc. The Chemlstry of Coal
Utllzatlon)' [Second expanded edition (2
ndSupplementary Volume)
, 1981]. In both gas generators, coal is fed intermittently from the top through a rock hole/f- to a distributor which continuously feeds the coal onto a fixed bed of coal and coal derived solids in a vertical shaft. Spread evenly.

As the coal descends through the shaft, it is first heated, dried and partially de-volatilized in the presence of hot gases rising from the base of the reactor.
tllllzed ) @ノLru. In the lower area of the floor,
ds-volatllllzed
) coal [i.e. char]
reacts with water vapor and oxygen and is converted to sulfur. The inorganic substances contained in the coal are discharged as dry ash in the gas generating furnace at a relatively low temperature maintained by the use of excess steam in the conventional Lurgi process. In contrast, in the method developed by Brittlsh Gas, the inorganic material is melted to form a mobile slag. This slag is drained from the fuel bed, quenched with water, and then discharged as a glassy frit.

Drying and devolatilization
The top of the fixed bed, where n ) occurs, is the I devolatilization zone (
do-volatllzatlon zone)
The lower part, where the coal char reacts with water vapor and other reactions occur, is known as the sourization zone. In a slagging reactor, water vapor and oxygen are injected all the way through the tuyere, and the intense reaction zone in front of the tuyere is known as the raceway. This is where charcoal oxidation dominates, providing sufficient temperatures to melt the inorganic materials and form a mobile slag.

In both gas generators, the gasification of coal contains tar (a hydrocarbon more dense than water), oil (a hydrocarbon less dense than water), naphtha (a low-boiling oil fraction), and phenolic concentrates. , yielding a range of by-product acidic organic liquids. Apart from representing a waste of material that would have been more useful if converted to gas, these by-products pose an environmental threat as the scale of contemplated coal gasification projects grows larger. The cumulative effects of these by-products in the process are becoming an increasingly important consideration.

It is thus very desirable to send the liquid by-product back to the gas generator in such a way that it is completely gasified.

It is common practice to recirculate tar to the top of the bed of a fixed bed gas generating furnace to reduce dust carryover. Although this is done very effectively, the tar that has already passed through this part of the gas generator is distilled from the top of the bed with little or no decomposition, so that the tar net yield will not decrease.

Westfield Develop Center of Pritish Gas
entCenter) demonstrated complete slagging of tar and oil by injecting the tar and oil through tuyeres into the raceway region of a slagging reactor. It is expected that similar injections of naphtha and phenols will be fully viable and similarly effective in gasifying them to complete depletion. The temperature in the raceway is so high that the inorganic components of the coal are released as molten slag into the slag dales below. Such high temperatures ensure that almost all the carbon in the coal is converted and no more than traces of oxygen are left in the slag. In this case, no recycled organic material remains.

However, a very serious drawback of this method is.

The oxygen consumption of gas generating furnaces is greatly increased, both in terms of heat output and more specifically coal input. This is believed to be due to the overriding requirement of maintaining a temperature that produces a slag of suitable viscosity to enable slag tapping with proven technology.

The present invention seeks to alleviate the drawbacks of increased oxygen consumption associated with the injection of tars, oils, and phenols through the tuyere of a sludge-producing furnace.

Therefore, the present invention provides for supplying a gasifying agent containing water vapor and oxygen into the bed through the entire tuyere leading to the raceway located below the fixed bed, and to reduce the condensation caused by the sulfurization of the coal.
Fixed-bed ash slagging is a method of coal slagging in a smelting furnace that recirculates non-aqueous materials to the coal bed, below the bed, but above the raceways; Coal provides a sulfurization process characterized by recycling at the point where the bed temperature is sufficient to gasify the material.

Above the raceway, there is a more stable region of coal char particles that descend down the bed in a fairly uniform and steady manner in a free-flowing manner relative to the hot gases.
), the turbulence and intensity of the combustion is overcome by the oxidation reaction. Much of the heat released in the combustion zone is carried into this region as sensible heat by the rising gases, supporting the endothermic reactions described below.

The gas is cooled by these reactions, and as the gas rises, the bed temperature decreases from 1600-1800°C to about 1
000°C, and the reaction rate becomes low. Eventually, the gas and char temperatures are no longer sufficient to support any further endothermic reactions, and the gasification process effectively stops, creating the upper boundary of the gasification zone. The temperature at the upper boundary of the gasification zone is much higher in a slagging furnace than in a dry-bottom furnace.

Drying and devolatilization occurs in the top of the bed and causes further cooling.
) The reaction is completed well above the upper boundary of the gasification zone. Therefore, within the fuel bed of a slagging gas generator there is a substantial area where the temperature is sufficiently high to ensure that the recycled tar, oil, and phenol react quickly. When these byproducts are injected into this region, they do not cool the raceway zone and do not interfere with slag formation. Thus, there is no need to significantly increase oxygen consumption.

The products produced by the reaction of the recycled by-products with the hot gas depend on the injection point selected. Introduction into the gasification zone primarily results in conversion to carbon monoxide and hydrogen, while introduction further up the cooler bed allows hydrocarbon gases such as methane to remain. However, when injecting into the top of the bed, not all of the liquid is broken down, thereby increasing the overall liquid recirculation rate. Depending on the exact conditions and method of injection, a portion of the injected liquid is thermally decomposed into a solid carbonaceous precipitate which, along with the charcoal, migrates into the sulfurization zone and is gasified in the presence of water vapor.

The production of hydrocarbons such as methane from recycled liquid byproducts is particularly advantageous in the production of alternative natural gas (5NG) because it is less endothermic than the production of carbon oxides and hydrogen. In this case, the gas generator outlet temperature increases with little or no effect on oxygen consumption.

EXAMPLE The invention and the benefits derived therefrom were demonstrated by slagging British coal at a steam/oxygen molar ratio of 1.3 using 98% pure oxygen at an r-di pressure of 31 par in a gas generating furnace. [Rossington (Ros-5lngton)]
K is shown by gasification.

Relevant data are shown in Table 1. Nine comparative data are shown in column (1) of Table @1 for operations without recirculation of liquid by-products, and data for operations with these by-products injected through the tuyeres into the raceway zone. (2) Show profit.

(In the production of carbon steel shown in the 1+ column, dry/uncharcoal content [dr
y, ash-free (d, a, f, ) ]
On a standard basis, a mixture of tar, oil, and naphtha is obtained as a by-product at a rate of 0.066 g/g/g/g of the coal feed. This mixture is dissolved in the raceway (
2) As shown in the column, when injecting through the tuyere, the water vapor and oxygen consumption for the coal feed is 10
It can be seen that the amount increases by more than .

Of course, the gas yield is increased, but the product gas calorific value is slightly lower F because gas oxidation in the raceway does not result in methane production. The extra oxygen consumption results in an exit temperature increase of over 50%.

EXAMPLE 1 This example [see column (3) of Table 1] shows that the required increase in oxygen consumption when the liquid by-product is recirculated and injected approximately midway into the top of the fixed bed in accordance with the present invention. is less than half the increase in i when injecting through the tuyere. A given product gas composition is approximately CJ,1 when the byproduct gasification rate is 0,0661cfJ/Ic9.
It was obtained through recirculation. That is, when the monolithic products are gasified at the same rate as they are produced, a portion is still not gasified when initially recycled.

As can be seen from Table 1, the calorific value of the product gas increases and only a smaller amount of methane needs to be produced in the subsequent methanation step, resulting in greater efficiency in the production of SNG. The benefits of methane production within the gas generator, as opposed to downstream methane production, can be seen as a reduction in dounce IJ-me equipment and heat losses and facility requirements associated with external methane production. The ratio of methane produced directly in the gas generator to the total amount that can theoretically be produced from the product gas provides a first indication of this benefit. This ratio is 31% for the product shown in (3) 4Il of Table 1. In the case without recirculation [(IL4)] and in the case of injection through the slats [column (2)], this ratio is 24% and 23%.

Example 2 In this example, recirculation is achieved in one pass by moving the injection point further down the bed than in Example 1 to a point above but close to the upper boundary of the gasification zone. Almost complete gas conversion of the by-products is achieved. This is for coal being gasified.

and more significantly in terms of heat output.
Provides extremely low oxygen consumption as seen in (4) 4FM in the table. The high methane content in the product stream, which reaches 40% of the amount that could be theoretically produced, reduces the work of methanation and thus gives a high conversion efficiency of coal to SNG. Another efficiency improvement.

Resulting from a higher outlet temperature, this higher outlet temperature increases water vapor production in the gas cooling system.

1 ]　2

Claims (1)

[Claims] (1) A sulfurizing agent containing water vapor and oxygen is supplied into the fixed bed through the tuyere leading to the raceway located below the fixed bed, and the condensable non-condensing agent produced by the gasification of coal is Water-based substances to the bottom of the floor. However, above the raceway, the coal is recirculated at a point where the bed temperature is sufficient to gasify the material. .