JPS5851037B2 - Tarbunnadoofukumukoongasunoreikiyakuhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for cooling high-temperature gases with a high tar content to recover high-quality heat and steam.

Various methods of partially combustion gasifying liquid or solid hydrocarbons with a large residual carbon content, such as heavy oil and coal, have been studied from the viewpoint of pollution prevention.

This is a method that partially burns fuel at a temperature of 1000℃ or higher, and then desulfurizes it after cooling.The resulting gas is CO, CO2, and N.
2. It is made of N2 and has a low calorific value.

However, in this method, the boiler for cooling the high-temperature gas generated in the gasifier and recovering sensible heat requires burnout of the heat exchanger tube at the gas inlet, coking of the heat exchanger tube at the outlet,
Furthermore, there are problems such as erosion, and there are many structural problems in increasing the size.

In addition, heavy oil, olefins produced by thermal decomposition of asphalt,
In the production of aromatic hydrocarbons and the production of SNG by coal gasification, the temperature of the gas from the cracking furnace or gasifier is below 1000°C, but the amount of tar and coke is large, and it is similar to that of a boiler. Indirect cooling using heat transfer tubes causes clogging during heat transfer due to coking, resulting in a rapid decrease in cooling capacity, while direct cooling using oil or water inevitably reduces the quality of recovered heat, such as temperature and pressure. Improvement is desired.

And Special Publication No. 46-34006, Special Publication No. 469322
The publication proposes a method of recovering thermal energy from hydrocarbon pyrolysis gas using a molten heat medium or a high boiling point liquid medium, and it is expected that this method will improve the quality of the recovered heat. However, there are difficulties in separating and removing coke and tar in the heating medium.

In addition, Japanese Patent Publication No. 46-15780 proposes a cooling method in which gas is blown into a fluidized bed using solid particles as a fluidizing medium and water or low boiling point oil is sprayed into the bed.

Although this is effective in preventing tar troubles and separating coke and tar from gas, it does not take into account the recovery of sensible heat from the gas, and from the description it is clear that heat recovery is extremely insufficient. However, there are drawbacks such as increased burden due to condensation of water or oil.

The inventors of the present invention will cool high-temperature gas rich in coke and tar obtained from liquid or solid hydrocarbons with high residual carbon such as heavy oil and coal without coke or tar druffle, and recover high-quality heat and steam. The present invention was achieved as a result of repeated research in order to provide a simple method and device for this purpose.

That is, the present invention uses a fluidized bed to cool gas containing tar, coke, etc. produced by high-temperature treatment of liquid or solid hydrocarbons such as heavy oil and coal that contain residual carbon. is not provided directly above the part where the high-temperature gas is jetted, but is provided in the region of the peripheral wall of the fluidized bed where particles descend into a downward flow.

(2) Maintain the fluidized bed temperature so that it does not fall below 350°C.

(3) The jetting speed of high temperature gas into the fluidized bed is 15 m/sec or more, and the fluidization speed is 1 m/sec or more.

This invention relates to a method for preventing tar druffles and recovering high-quality heat.

The fluidized bed is filled with refractory particles and/or coke particles produced by thermal decomposition and, if necessary, quicklime or limestone particles as a fluidizing medium.

The fluidized medium particles perform the following functions in cooling the high-temperature gas containing tar and coke according to the present invention.

(a) It is excellent as a heat transport medium, contributing to uniformity of temperature throughout the layer, heat transfer between gas and cooling pipes, etc.

(b) Since it is in an almost completely mixed state and can store a large amount of heat uniformly, it has a buffering effect against small fluctuations in gas amount and temperature, and provides particularly favorable conditions for tar substances that are sensitive to temperature. Maintain stability.

(c) As a stable collection medium for tar substances, fluidized media particles are far superior to liquid media, given appropriate values for temperature and flow.

That is, the condensed and deposited tar substances change into stable coke and gas within the temperature and flow range of the present invention, and do not cause problems such as agglomeration of particles and fouling of cooling pipes.

In addition, tar and coke introduced into the fluidized bed along with high-temperature gas condense on the surface of the fluidized medium particles as the temperature decreases.
Deposit.

In this case, the fluidized state of the particles and the fluidized bed temperature have the following effects on the stability of the fluidized bed and the collection of tar.

(B) Fluidization state of particles When high-temperature gas is ejected into a fluidized bed, the high-temperature gas comes into contact with a low-temperature fluidized medium, causing a rapid drop in temperature and condensation of a large amount of tar near the ejection port. In order to prevent agglomeration and poor fluidization, the ejection speed needs to be above a certain value.

Gases containing tar, fluidized media particles with tar on their surfaces,
In a fluidized bed with cooling pipes where tar is easily deposited, the fluidization speed must also exceed a certain value in order to ensure stable fluidization and prevent tar deposition on the cooling pipes (so-called coking).

To summarize these, the gas ejection speed at the ejection port and the so-called fluidization speed have the following significant effects on the flow of gas particles, and the accompanying agglomeration of particles and the presence or absence of flow deterioration.

(b) Temperature of the fluidized bed The gas generated by high-temperature treatment of liquid or solid hydrocarbons with a high residual carbon content, such as heavy oil and coal, contains high-boiling point residual oils and tar as well as volatile components with a wide boiling point range.

Moreover, these substances are of course stable at low temperatures, but at high temperatures they liberate low molecules while polymerizing and turning into polymers.

This phenomenon becomes noticeable when the temperature exceeds around 350°C, and causes the following effects on gas cooling.

The present invention will be explained with reference to FIGS. 1, 2, and 3.

Figure 1 is a cross-sectional view common to Figures 2 and 3;
3 are schematic diagrams showing examples in which the direction of gas ejection from the ejection port 4 is upward and downward, respectively.

A cooling pipe 3 is installed along the inner lining 2 of the circular fluidized bed casing 1.
, and a high-temperature gas outlet 4 is arranged at the center.

Providing the cooling pipe 3 along the lining 2 in this way means that
This is particularly preferable since it does not interfere with the fluid state.

The cooling pipe 3 is immersed in a fluidized bed 11.

The fluidized medium particles filling the fluidized bed 11 are fluidized by high-temperature gas ejected from the ejection port 4 produced by high-temperature treatment of liquid or solid hydrocarbons such as heavy oil or coal in a device (not shown). be converted into

As mentioned above, the cooling pipe 3 is immersed in the fluidized bed 11, and comes into contact with the particles that move violently to cool the particles with a high heat transfer coefficient.

At this time, the water that entered the cooling pipe from 3' comes out as steam from 3".

Also, the particles are substantially uniform in temperature throughout the layer due to intense mixing.

The heat exchange rate between gas and particles is extremely low, and fluidized bed 11
The temperature of the gas leaving is approximately equal to that of the particles.

In this way, the sensible heat of the gas is given to the internal fluid through the particles and the wall of the cooling pipe 3, achieving high-quality heat recovery.

Incidentally, since particles and dust fly out from the fluidized bed 11 along with the gas, they are collected and separated by the cyclone 6 following the gas conduit 5.

The gas from the cyclone 6 is led through a gas conduit 7 to the next cooling and purification stage, not shown.

Since the particles accumulate and become coarse due to the deposition of coke, they are sent to the next combustion regeneration step (not shown) through the particle discharge pipe 10.

Further, if necessary, the particles are made up through the particle conduit 9 and returned through the particle supply tube 8.

It is also possible to add lime or the like for desulfurization.

Example I C heavy oil was subjected to partial combustion cracking under the following conditions.

Gasification conditions C Heavy oil composition (wt%) C: 84.6, H: 12.3, O: 0.48, N: 0.
14, S; 2.24 Air/C heavy oil (Nm:/l): 0.16 Stimium/C heavy oil (kg/l); 0.40 Temperature; 820
'C pressure crab 1.5 kg/cmG The composition of the obtained generated gas is as follows.

Produced gas composition (wt%) H2; 0.7.02; 1.0. N2; 40.
2, CO; 12.7, CH4; 6.3, C2H4;
9.7, C2H6; 0.6, C3 or higher; 19.0 The produced gas was then cooled under the following conditions.

Cooling conditions Temperature: 380°C ± 20°C, Pressure: lky/cvtG particles: Coke 1 φ, Fluidization speed: 1.5m/sec Gas ejection speed: 1sm/sec, Bed height: 1.677L As a result, 4
Able to drive for more than 0 days without any problems, 10
Saturated steam of 0 kg/cntG was collected.

The amount of coke produced is 0.27k per 1kg of C heavy oil.
It was g.

It should be noted that under conditions other than those of the present invention, agglomeration of particles due to tar frequently occurred, making it difficult to continue operation for more than 10 days.

Example 2 Coal was gasified under the following conditions.

Gasification conditions Coal composition (wt%) C: 86, H: 3.7, S: 0.3, ash content: 10 Stim/coal: 1.66, temperature: 820°C, pressure: 20
kg/crAG The main body of the equipment is a pair of two units (one is a gasification furnace, the other is a CaO regeneration furnace) that circulates a slurry made by dispersing lime in molten salt.
It consists of a furnace.

The resulting gas had the following composition.

Generated gas composition (Vo1%) H2; 34.4, Co; 18.4, Co2; 10.4
, CH4; 20.7, H20; 16.1 The product gas was then cooled under the following conditions.

Cooling condition temperature: 400℃±20℃, pressure: 20 kg/cr
lG fluidization speed: 1.5 m/sec, gas ejection speed: 20 m
/sec, bed height: 2.5 m As a result, it was possible to operate for more than 40 days without any problems, and 120 kg/cAa of saturated steam could be recovered.

The amount of coke produced is approximately 0.19 k per 1 kg of coal.
It was g.

Note that, as in Example 1, cooling using a fluidized bed was extremely difficult under conditions other than the conditions of the present invention.

Example 3 Petroleum was pyrolyzed under the following conditions.

Pyrolysis conditions Crude oil type: Khafji, Conradnon carbon; 6.8% steam/crude oil (kg/kg); 1.0 temperature; 850'
C1 pressure crab 1.5 kg/crirG The main body of the apparatus consists of a pair of two furnaces that circulate coke particles between a pyrolysis furnace and a coke combustion furnace.

The composition of the resulting gas is as follows.

Produced gas composition (wt%) H2; 1.5, CO; 3.2, Co2; 4.3, CH
4;16.0. C2H2; 1.1, C2H4; 2
8.0, C2H6; i, s, C3H8; 0.6, C
, H6; 4.7, C4; 38.7 Then, the generated gas was cooled under the following conditions.

Cooling conditions Temperature: 400℃±20℃, pressure: 1 kg/crit
G particles: φ between coke particles, fluidization speed: 1.5 m/s, gas ejection speed: 20 m/s, bed height: 2.5 m.As a result, it can be operated for more than 40 days without any problems,
Saturated steam of 100 kg/critG could be recovered.

Note that the amount of coke produced was 0.15 kg per 1 kg of crude oil.

[Brief explanation of drawings]

1, 2, and 3 show examples of apparatus used in the present invention.

Claims (1)

[Claims] 1 When high temperature gas containing tar etc. is cooled in a fluidized bed equipped with a cooling pipe inside to recover heat and steam, the cooling pipe is not installed directly above the part where the high temperature gas jets, and the fluidized bed is equipped with a cooling pipe. A cooling pipe is provided in the downflow generation area of particles on the bed peripheral wall, the temperature of the fluidized bed is maintained not to fall below 350°C, and the jetting speed of high temperature gas into the fluidized bed is set at 15 m/sec or more.
A method for cooling high-temperature gas containing tar, etc., characterized by setting the fluidization speed to 1 m/sec or more.