JPS5915956B2 - Coal carbonization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for carbonizing coal, and more particularly to a method for carbonizing coal, and more specifically, low-temperature carbonization of coal by fluidized solid technology, thereby achieving high B
The present invention relates to a method for obtaining increased yields of oil and tar while producing TU by-product gas.

No. 3,140,241 and No. 3,140,242 to Work et al., a mixture of reactive coal combustion and a pitch binder is formed into briquettes, and the resulting green briquettes are oxidized. harden in an atmosphere,
It is described that the cured briquettes are then coked in an inert atmosphere to reduce the content of volatile substances to less than about 3%.

This product is a highly reactive, physically strong carbonaceous material that is excellent for use in metallurgical furnaces, including iron smelters.

For example, during commercial blast furnace operations, these briquettes have shown generally equivalent performance to conventional high temperature furnace coke.

In fact, these briquettes were superior to high temperature furnace coke in that their uniform size and shape tended to facilitate furnace operation.

The reactive coal combustion material used in the production of the above-mentioned shaped coke briquettes is a granular amorphous carbonaceous material whose surface contains carbon derived from coal tar pitch or other such bituminous binder and then is particularly susceptible to the formation of strong carbon-carbon bonds due to the formation of strong internal three-dimensional bonds.

The extraordinary strength and uniformity of this briquette is due to this surface affinity.

The reactive coal combustion product described above is obtained by heating coal particles in three different stages under conditions that cause the release of tar-forming vapors.

Preferably this heating takes place in a fluidized bed.

In the first or catalytic stage, the coal is heated in the presence of oxygen to a temperature below the temperature at which tar-forming vapors are released.

Heating of the coal particles in the fluidized bed can be carried out by burning a small portion of the coal, or by sensible heat in the fluidizing medium, or alternatively by indirect heat exchange.

The catalyzed coal is then heated in a second or carbonization stage to release tar-forming vapors and produce coal (c
har ) particles.

The fluidizing atmosphere contains sufficient oxygen to provide the desired temperature through partial combustion of the coal, typically a temperature below about 649°C.

Oxygen is introduced into the fluidized bed in the form of air as a component of the fluidizing medium.

The remainder of the fluidizing medium can be any gas that does not react with the coal particles at this stage.

Carbonized coal,. or char then the third
or during the combustion stage to give the final reactive coal shell burnt product.

Preferably the combustion is carried out at a sufficient temperature, i.e. from about 60°C to about 8°C.
This is done in a fluidized bed operated at 71°C to reduce volatile components in the final product to less than about 5%.

Heat is provided by limited combustion of charcoal. Wo r
According to the aforementioned patent to K. et al., the fluidizing atmosphere is substantially inert except for the presence of oxygen in an amount required by the rate of oxidation of the char necessary to supply the heat demands of this step. It is a gaseous medium.

Preferably the fluidizing atmosphere is air or a mixture of air and flue gas.

The binder for shaped coke briquettes is preferably obtained by processing the cool recovered from the carbonization of the coal described above.

Such treatment reduces the tar's moisture content to 0.5% by aerating it and lowers its softening point to about 55°C.
65°C (ASTM Ring and BaII
).

The shaped coke of the Work et al. patent can be made from a wide variety of coal types, including non-coking coals such as lignite, thereby providing the metallurgical industry with an alternative to conventional furnace coke. do.

This feature is particularly attractive to coke users in areas where metallurgical coals do not have deposits of non-coking coal.

However, even when metallurgical coal is readily available, processing it in a conventional high temperature coking oven is not economically straightforward due to the need for expensive environmental control systems.

In fact, pollution elimination adds so much to the capital investment of a coking operation that steelmakers in affected areas may prefer to avoid coking rather than incurring significant costs for new plant and equipment that can meet stringent emission standards. There will be an increasing trend towards importing.

In contrast, the process of the Work et al. patent is inherently non-contaminating, thereby minimizing the need for costly cleaning equipment installations.

Even now, molded coke briquettes are manufactured by this method in plants that meet US federal and state environmental regulations and likely meet standards in most other countries.

Despite its apparently superior metallurgical properties,
Work et al.'s shaped coke has not met commercial acceptance, and that appears to be well-founded.

This can be almost entirely attributed to two manufacturing defects.

One is about 550 BTU of intermediate BTU coke oven gas.
The by-product gas has a heat content of about 130-170 BT, U/m3 compared to a heat content of
S'CF (484X10'~633.4xl O4J/
Due to its low heat content of 7F+”).

This condition results from the use of air as a fluidizing and oxidizing atmosphere at various stages of the process.

The nitrogen in the air is inert and passes through the fluidization vessel;
It is considered a component of byproduct gas.

The heating value of this by-product gas is greatly reduced by the presence of nitrogen.

Until the time of the energy crisis, low BTU byproduct gases were not an important factor in deciding whether to replace a substantial proportion of conventional coke capacity with the shaped coke of Work et al.

Natural gas and oil could be purchased inexpensively in virtually unlimited quantities to meet the fuel requirements of steel mills.

However, with today's energy prices and availability, there is a need to provide by-product gases of increased heating value in combination with shaped coke production.

Another criticism leveled at the formed coke of Wo r k et al. is that the process generally does not produce enough tar to meet the internal binder requirements of the plant.

When this occurs, a suitable external binder, such as high temperature pitch, must be produced to compensate for the deficiencies of the internal binder (G).

The yield of this binder naturally depends on the type of coal to be treated.

For example, certain bituminous B rank coals, such as Ercole Adabilsweem from Kemmerer, Wyoming, USA, are generally self-sufficient in binder.

Other ordinary bituminous coal B rank coal such as Inori/
i66 gives low yields of tar and does not provide enough autogenous binder.

In such cases, the missing amount of binder must be produced from external sources, usually high temperature furnace pitch.

Just as low BTU by-product gases were not an important factor in evaluating Work et al.'s shaped coke prior to the energy crisis, the need to obtain supplemental binder was also not an important factor.

However, the price of hydrocarbons derived from coal has skyrocketed.

And the pitch binder is from 20~20 before the energy crisis.
Approximately $200/US ton (9
07ky).

Clearly, in today's energy climate such ancillary factors are important in evaluating the commercial prospects of shaped coke technology.

According to the present invention, reactive drying, tar and high BTU
An improved method of fluidized bed pyrolysis of coal to produce gas is provided.

8. Heating the coal particles in a first fluidized bed under oxidizing conditions to a temperature above about 121°C and below the temperature at which a substantial amount of tar-forming vapor is released; B. further heating the product of step A to the carbonization temperature in a second fluidized bed to release substantially all tar-forming vapors from the product. to produce tar, charcoal, and carbonization gas, and heat the charcoal from Step B in a third fluidized bed to reduce the volatile content of the charcoal to less than about 5% to form a reactive dry calcined product. and producing a dry calciner gas, the method comprises introducing recycled carbonization gas into step B at a temperature below its pyrolysis to provide a fluidizing atmosphere, and introducing hot recycled dry calcined material into step B. Improvements are made in providing heat for carbonization, thereby resulting in higher BTU carbonization gas and increased tar yield.

Therefore, a major advantage of the present invention is a low temperature carbonization process for coal under fluidized conditions that releases volatiles from the coal to produce reactive burnt products, increased tar yields and high BTU by-product gases. Our goal is to provide the following.

A further advantage of the present invention is a fluidized bed carbonization process for bituminous, sub-bituminous and lignite grade coals for the release of volatile substances from the coals to produce metallurgical shapes from reactive baked goods and from said baked goods. A high BT
It is an object of the present invention to provide a method for producing U while generating by-product gas.

Other advantages will become apparent from the description below.

In the practice of the present invention, coal is pulverized, for example in a hammer mill, to a fluidizable size, and is introduced into a first fluidized bed where it is heated under oxidizing conditions to eliminate its tendency to agglomerate. reduce

The fluidizing medium is preferably steam or flue gas with air to provide the necessary oxidation.

Heating of the coal particles in the fluidized bed can be carried out by burning a small portion of the coal, or by sensible heat introduced into the fluidizing medium, or alternatively by direct heat exchange.

The fluidized bed is approximately 121°C to 2°C for non-coking coal.
Typically held at a temperature of 60°C, for coals with coking and caking properties the temperature is approximately 2
It is in the range of 60°C to 427°C.

The maximum temperature is the temperature at which tar vapor is released.

Coal particles from the first fluidized bed are forced into a second fluidized bed where they are heated until all tar vapor is released.

The lower temperature limit is the temperature at which the coal releases a large amount of tar-forming vapor, and this temperature is the upper temperature limit for the first stage of heating, approximately 427°C for coking coals and about 427°C for non-coking coals. is approximately 260°C.

The upper temperature limit is the temperature above which cracks, cracks, and foaming occur to the extent that expanded coal particles cannot return to their original coal particle size and shape.

This upper temperature limit is approximately 621°C to 649°C.

Generally, the higher the carbonization temperature (within a lower and upper limit), the greater the amount of tar produced.

The charcoal particles from the second or carbonization stage are further heated to reduce the amount of volatile materials therein to less than about 5%.

Desirably, the shell calcination is conducted in a fluidized bed at the minimum temperature necessary to achieve this reduction, that is, from about 760°C to 871°C, with a residence time of about 7 minutes to about 60 minutes.

This fluidizing atmosphere should be free of reactive gases such as carbon dioxide or water vapor, and oxygen can only be tolerated in such amounts that it is consumed by the oxidation of the charcoal in supplying heat to this stage.

As previously noted, the heat for carbonization in the Work et al. method is provided by the oxidation of the carbonaceous components in the reactor with oxygen (usually in the form of air as part of the fluidizing atmosphere). .

As a result, the by-product gas recovered from the carbonizer contains a significant amount of nitrogen, resulting in a heating value of approximately 150 BTU/f.
t3 (558xlO'J/m') or less, which is undesirably low.

Moreover, oxygen in the fluidizing medium preferentially reacts with tar-forming hydrocarbon volatiles, reducing tar recovery to 30-50% of the amount available from a given coal.

For most coals, tar recovery is less than that needed to provide the amount of binder needed to make metallurgical coke from reactive calcined products.

According to the present invention, the above-mentioned drawbacks can be overcome by implementing but modifying the method of Work et al.

That is, in the present invention, hot recycled calcined material is used to provide heat to the carbonization stage of coal pyrolysis, and this is accomplished using recycled carbonization gas in the fluidizing medium.

Heating of the recycled desiccant is conveniently done by withdrawing some of the low BTU desiccator gas and combusting it in a heater, passing an oxidizing gas through the heater, and then introducing the heated gas into the desiccator. The obtained combustion heat then provides the heat for the dryer and the heat load for the recycled dryer.

Preferably, the oxidizing gas is air heated to 816°C.

Use of this method results in about 50% to 100% more tar increase than in the prior art described above, and at the same time 900 to 100 OBTU/ft3 (335,
A by-product gas in the form of carbonization gas having a heating value of 3.times.10@5 to 372.6.times.10"J/m" is supplied.

This is 150 when using air to provide heat for carbonization.
BTU/ft3 (558x10'J/rl)
It should be compared with

The total heating value of the by-product gases generated is 1 US ton of dry coal (9
Approximately 900M BTU (9.5X1
05 units) to 1.5MM BTU (1,6X1
This can also be seen as an increase to 0.06 joules).

In an embodiment of the method of the invention, 2000 lbs. (907 lbs.
, 2 to 9) is pulverized to a size suitable for fluidization, typically a size that passes through an A14 sieve (US sieve series ASTM E-11), and then fed to the first fluidized bed. Pre-process by

The coal is fluidized at this stage with a mixture of flue gas and air.

The temperature of the first fluidized bed is maintained at about 288°C.

The heat for this stage is provided by the combined sensible heat of the flue gases and the oxidation of the coal by the oxygen in the fluidizing atmosphere.

Oxidation of the coal helps reduce its agglomeration, but is limited to the extent necessary to prevent agglomeration when subjected to higher temperatures in subsequent processing steps.

Approximately 1% of non-aqueous volatiles are removed from the coal during a residence time of approximately 30 minutes.

This pretreated coal in an amount amounting to approximately 1,980 bonds (898,1 to 9I) is then fed to a second stage where it is subjected to a carbonization temperature of 496°C and substantially all of the tar-forming vapors are removed. It is held at this temperature until released, typically about 20 minutes.

After carbonization, the produced coal in an amount amounting to about 1,540 pounds (698,5 kg) is introduced into a third or smoldering stage where it is heated at a temperature of about 816° C. to a maximum volatility of about 5%. Produce smoky charcoal or smoked products with substance content.

The yield of smoked food is approximately 12□00 pounds (544.3 Yu).

A portion of the smoker gas is withdrawn from the main stream and divided into two parts for internal use.

One part is combusted with air in a heat exchanger.

This heat exchanger heats the carbonization gas recycle stream to 538° C., which is used to fluidize carbonization stage 2 and to provide a portion of the heat for carbonization.

Another portion of the smoker gas is combusted with air in a second heater.

A stream of air passes through this second heater to 816°C.
The heated air then blows into the smoker, where the heated air combusts the fuel values in the smoker to provide heat for the smoker and for recycling and drying.

The ratio of recycled dry roast to coal feed is approximately 0.5~
About 0.7 is preferred.

The recycled carbonization gas and recycled dry calcinations together meet the heat requirements of carbonization stage 2.

The carbonizer overhead from stage 2 passes through a condenser where the tar is removed leaving a high BTU carbonization gas which is recovered.

Flue gas from a heater can be introduced into stage 1 to provide heat and a fluidizing atmosphere.

Referring to Table 1, there is shown, on the one hand, that Work et al., U.S. Pat. '140,241, on the other hand, using a modified version of the carbonization method of the present invention,
The results are shown when 1 US ton of molded coke was produced from each of the smoky product produced by thermal decomposition of 166 sub-bituminous coal B and a bituminous coal binder.

The process of the present invention produces 0.26 US tons (235,9 kg) of binder material compared to the conventional Work
According to their method, 0.12 US tons (108,9!9
It will be observed that only the binder material of ) is changed.

That is, the method of Work et al.
The present invention provides a binder surplus of 0.08 US tons (72.6 kg), whereas the present invention provides a binder surplus of 0.08 US tons (72.6 kg).

The low BTU carbonized gas of Work et al. has a value of only $1.50 (coal equivalent), whereas that of the present invention has a value substantially equivalent to pipeline gas.

The only loss resulting from the practice of the present invention is the reduction in the output of the smoker gas due to its use as a fuel to heat the recycled burnt and carbonizer fluidizing gases.

However, the use of such low grade by-products results in a reduction of 27.2 kg per 907.2 kg of coal provided by the process of the invention.
It is readily apparent that $50 is a small price to pay for achieving an overall cost advantage.

It is noted that all of the heat for carrying out the fluidized bed coal pyrolysis of the present invention is derived from the combustion of the smoldering furnace off-gas and that even the heat of the pre-treatment stage can be supplied by the flue gas from the smoldering gas burner. It should be pointed out.

No additional smoke consumption is required to heat the recycled dry roast, and this extra heat load comes from burning the smoke with air at 816°C.

Approximately 1200 lbs.
of smoked food can be obtained from 1 US ton of coal.

That is, the provision of high BTU byproduct gas and increased tar yield by the process of the present invention is not obtained at the expense of reduced output of fixed carbon values.

Claims (1)

[Claims] 1. Steps: A. Bringing particles of coal under oxidizing conditions in a first fluidized bed to a temperature above about 121° C. and below the temperature at which a substantial amount of tar-forming vapor is released. heating to produce a non-agglomerated product in a subsequent step B; and B further heating the product of step A to the carbonization temperature in a second fluidized bed to remove substantially all tar formation from the product. The charcoal from Step B is further heated to a higher temperature in a third fluidized bed to reduce the volatile matter content of the charcoal to less than about 5%. producing a reactive calcined product and a dry calciner gas by fluidized bed pyrolysis of coal,
In a method for producing tar and carbonization gas; the recycled carbonization gas is introduced into step B at a temperature below its thermal decomposition to provide a fluidizing atmosphere, and the hot recycled dry roasted material is introduced into step B to provide heat for carbonization. . A process characterized by a high BTU carbonization gas and an increased tar yield. 2. The method according to claim 1, wherein the heat of the hot recycled drying product is derived from the combustion heat of the drying furnace gas. 3. The method of claim 1, wherein the coal is selected from the group consisting of bituminous coal, sub-bituminous coal, and lignite. 4. The following steps: A. Heating the particles of bituminous coal in a first fluidized bed under oxidizing conditions at a temperature of 121° C. to 427° C. to produce a non-agglomerated product in the next step B; further heating the product of A in a second fluidized bed to a carbonization temperature not exceeding about 649° C. until substantially complete removal of tar-forming vapors has occurred to produce tar, charcoal, and carbonization gas; and heating the charcoal from Step B to a higher temperature in a third fluidized bed to reduce the volatile content of the char to about 5% or less to produce a reactive calcined product and a calcined furnace gas. , in a method for producing reactive desiccant, tar and carbonization gas by fluidized bed pyrolysis of bituminous coal; introducing hot recycled carbonization gas into step B at a temperature below its pyrolysis to provide a fluidizing atmosphere; and introducing the hot recycled dried roasted material into step B to provide heat for carbonization.
A process characterized by a high BTU carbonization gas and an increased tar yield. 5. The temperature of step A is about 288°C, the temperature of step B is about 496°C, and the heat of the hot recycled dried roast is derived from the combustion heat of the roasting furnace gas. the method of. 6 The heat load for carbonization is induced by withdrawing the furnace gas, one part of which is combusted in a heat exchanger to heat the carbonization gas, and another part of the furnace gas The part is combusted in a heat exchanger to heat the oxygen-containing gas entering the fluidized bed in step C, where sufficient combustion material is oxidized to provide the heat load of the combustion furnace and the recycled shell burnt material. The method according to claim 5. 7. The method of claim 6, wherein the oxygen-containing gas in step C is air heated to about 816°C. 8 The ratio of recycled roasted food to coal feed is approximately 0.5~
8. The method of claim 7, wherein the amount is about 0.7.