CA1208021A

CA1208021A - Method and means for gasifying carbonaceous material

Info

Publication number: CA1208021A
Application number: CA000414473A
Authority: CA
Inventors: Borje Johansson; Sven Santen
Original assignee: SKF Steel Engineering AB
Current assignee: SKF Steel Engineering AB
Priority date: 1982-03-01
Filing date: 1982-10-29
Publication date: 1986-07-22
Also published as: BR8206416A; NL8203909A; KR880000353B1; ATA364182A; DE3233774C2; PL239081A1; IN156382B; IT1153274B; DD208986A5; FR2522333A1; NO158066B; MX161612A; ES8400477A1; NZ202333A; PL135926B1; AU546482B2; AU9002682A; YU235382A; PH18531A; NO823341L

Abstract

ABSTRACT
"GASIFYING CARBONACEOUS MATERIAL"

In gasifying carbonaceous material to a gas mixture consisting primarily of CO and H2 and desirably having a total content of CO2 and H2 less than 12%, carbonaceous material in lump form is supplied via a sluice arrangement to a reactor from above to a predetermined filling level. The gas produced is withdrawn from the reactor at a level located below the upper surface of the carbonaceous material. Oxidant and/or thermal energy is supplied both above the surface of the carbonaceous material in lump form and also at a lower level in the reactor, located below the level of the gas outlet.

Description

~Z~102:L

DESCRIPTION
~IGASIFYING CARBONACEOUS MATERIAL"

The present invention relates to a method and means for gasifying carbonaceous material to a gas mixture consisting primarily of C0 and H2 and preferably having a total content of C02 and H20 less than 12~/o.
It has long been known to gasify carbon in shaft furnaces and retorts and also to perform partial gasification in conjunction with cokingO The drawback with the known methods is partly that it has been impossible to regulate the ratio between C0 and H2 in the gas produced but, most important, that the gas also contained a number of undesirable substances such as hydrocarbon, alcohols, phenols and tarO The latter is obtained primarily because the gasification takes place at low temperature, i.e. at temperatures lower than 1000C and under reducing conditions.
In order to remedy these drawbacks, other methods have been developed where the gasification takes place under high temperature and oxidizing conditions, such as the Koppers-Totzek method. However, this method has the disadvantage that, due to the thermodynamic equilibrium, the H20 content becomes ~ ~.

~2VY~

- 2 --relatively high which means that, -to enable it to be used for reducing iron ore, Eor instance, -the gas produced in this way must first be cooled, washed and then re-heated. Furthermore, the chances of influencing the ratio between CO and H2 leaving the gasifier is extremely slight according to this method.
In accordance with -the present invention there is provided a method of gasifying a carbonaceous material in a shaft furnace reactor to a gas mixture containing primarily CO and H2, which process comprises: 1) supplying a carbonaceous material in lump form to the shaft furnace reactor from above via a sluice arrangement to a predetermined filling level which is above the level of a gas ou-tlet; 2) supplying an oxidant in the ~orm of H2O, C2 or an oxygen-containing gas above the surface of the carbon-aceous material; 3) supplying an oxidant in the form of H2O, CO2 or an oxygen-containing gas into the reactor at a level below the level of said gas outlet so that partial combustion of the carbon-aceous material by the oxidant generates thermal energy at said level below said gas outlet, 4) supplying additional thermal energy at a level above the surface of the carbonaceous material with the aid of a plasma generator; 5) gasifying the carbonaceous material with the oxidant under a pressure exceeding atmospheric pressure to generate the desired gas ~ixture; and 6) withdrawing the generated gas mixture from the shaft Eurnace through the said gas outlet; wherein the thermal energy within the furnace is controlled such that the ash content in the carbonaceous material forms liquid slag which can be tapped off at the bottom of the shaft furnace.

, .

~z~

According to the method of the present invention, the gasification occurs at high temperature and under oxidizing con-ditions and at the same time the gas initially produced passes a hot bed of the carbonaceous material, e.g. coke or a coke-like material, whereupon its con-tent oE H2O reacts with carbon to form H2 and CO. Furthermore, the method according to the inven-tion makes it possible that the CO/H2 ratio is controlled since thermal energy is supplied via plasma generators so -that the ratio between H2O, CO2 and 2 in the oxidizing gas can be varied within wide limits.
The present invention also provides a reactor in the form of a sha-ft furnace for carrying out the above method com-prising (i) sluice arrangement at the top of the shaf-t for supplying the carbonaceous material in lump form in gas-tight manner to a predetermined filling level in the shaft, (ii) a slag-tapping means arranged at the bottom of the shaft, (iii) an annular drum provided with a qas outlet for withdrawing the pro-duced gas, said annular drum being arranged at a level below the predetermined level -to which the solid material is filled, (iv) a plasma generator for supplying thermal energy above the level of the solid material, (v) means -for supplyinq oxidant ahove the level of the solid material and below the level of the gas outlet, and (vi) means for supplying powdered carbonaceous material below the level of the gas outlet.
The invention will he described in more detail in the following with reference to two embodiments shown in the accompanying drawings, in which;

!

~.~o~z~

- 3a -Figure 1 is a diagram of apparatus according -to the invention, and Figure 2 shows an alternative embodiment oE the appara-tus shown in Figure 1 with respec-t to the lower part of the reactor.
The apparatus shown in Figure 1 and the alternative in Figure 2 consist of a shaft Eurnace 1, provided at the bottom with tuyeres 2 and plasma generators 3, preferably loca-ted symmetri-cally arouncl the shaft 1. These tuyeres are provided with feeding means for oxidant such as oxygen (or gas containing oxygen), H20 or C02 and possibly also powdered carbonaceous material. At a higher level the shaft 1 is provided with an annular drum 4 with a gas outlet 5 for the withdrawal of gas produced in the shaft. At the top the sha~t 1 is provided with a gas-tight sluice arrange-ment 6 for the supply of carbonaceous material in lump form and also with a tuyere for connec-tion of a plasma generator 7 and feed-in lances 8, 9 for ~2(~

oxidantO Supply means 11, 12 for the supply of extra oxidant if necessary open into the shaft at a level between the upper surface 10 of the solid material in the shaft 1 and the annular drum 4O To enable the process to be driven with liquid slag or solid ash, the bottom part of the shaft 1 i.s provided with either a tapping channel 13 (FigO 1~ for slag or a rotating feed-out table 1~ (FigO 2)o The apparatus shown in the drawings operates as follows:
- To achieve the desired gasification the carbonaceous material in lump form is fed in, possibly together with a sulphur-binder eOg. material in lump form cont~;n;ng Ca and/or Mg such as dolomite, via the sluice 6 into the shaft 1 to a predetermined level~
Thermal energy is supplied by means of one or more plasma generators 3 and 7, respectively, at the same time as oxidant such as 2~ C2 or ~2 is supplied via supply means 2 and 8, 9, respectively. The carbonaceous material in lump form, which may consist entirely or partially of coal, coke, pressed coke, peat, lignite, charcoal, wood or partially charred wood, etc., .is thus subjected to high temperature under oxidizing conditions, whereupon the vola-tile constituents are released and react with the oxidant producing primarily C0 and H2, while the non-volatile part is coked and forms a solid ~UB~Z~

cokelike product in lump form. It is desirable that an excess of oxidant is added in order to prevent the formation of soot. The oxidant supplied above the surface of the carbonaceous material should preferably 5 be sufficient at least to partially oxidise the volatile constituents of the carbonaceous material. Oxidant which has not reacted with the volatile constituents of the carbonaceous material will react lower down in the shaft 1 with the coke produced, forming additional CO
and possibly H2O. The products formed in the upper part of the shaft, above the level of the annular drum 4, are thus products similar to coke which continue down through the shaft and a gaseous product consisting primarily of CO and H2 which leaves the shaft 1 through the annular drum 4, which is preferably more than 50 cm below the level to which the carbonaceous material is filledO The temperature on the surface of the granular material in the shaft may reach about 2000C, while the gas leaving the shaEt via the annular drum 4 has a maximum temperature o~ 1500C. It is also possible to supply the necessary thermal energy by partial combustion of the carbonaceous material with oxygen instead of using a plasma generator. A number of tuyeres 2 are placed around the lower part of the shaft 1, said tuyeres being provided with either plasma generators or supply means for oxygen as well as supply ; .

~2~

means for oxidant and possibly powdered carbonaceous material and possibly also powdered material containing Ca and/or Mg to bind sulphur. At this level, preferably approximately lOOcm lower than the level of the annular drum 4, both the co~elike material falling down through the shaft and any powdered carbonaceous material blown in will be completely gasified. Any C02 and H20 leaving the reaction zone just before the tuyere will react further up in the shaft with the lump material on its way down, producing primarily CO and H2. The gas produced~ consisting primarily of CO and H2, will leave the shaft through the annular drum 4.
The gasification -takes place under a pressure exceeding atmospheric pressure.
It may be advisable to supply slag-former at this level through the material lances 2, and to regulate the viscosity and melting point of the slag and/or sulphur absorbants containing Ca and/or Mg, such as dolomite powder. By controlling the composition of the slag in this way, it can be made suitable as a raw product for the manufacture of cement. It is also possible to replace the supply of heat via plasma burners at this level by partial combustion of the carbonaceous material by means of oxygen.
If it is desired to produce a liquid slag from the ash content so that it can be tapped off, the ,, 1 ~l2~

temperature in the reaction zone in fxont of the tuyeres 2 in the lower part of the shaft should be maintained at above 1600C~ Preferably such liquid slag is granulated and rapidly cooled as it is being tapped off. When running the plant with solid ash which can be fed out as a solid by-product, this temperature should be kept below 1400C. Control of the supply of thermal energy enables these temperatures to be controlled.
The method described here for gasifying carbonaceous material offers considerable possibilities for regulating the H2/CO ratio in the gas produced, partly since the ratio of CO2/H2O in the oxidant can be regulated and partly by sharing the heat supply between partial combustion and via plasma generators.

::.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of gasifying a carbonaceous material in a shaft furnace reactor to a gas mixture containing primarily CO
and H2, which process comprises:
1) supplying a carbonaceous material in lump form to the shaft furnace reactor from above via a sluice arrangement to a predetermined filling level which is above the level of a gas outlet;
2) supplying an oxidant in the form of H2O, CO2 or an oxygen-containing gas above the surface of the carbonaceous material;
3) supplying an oxidant in the form of H2O, CO2 or an oxygen-containing gas into the reactor at a level below the level of said gas outlet so that partial combustion of the carbonaceous material by the oxidant generates thermal energy at said level below said gas outlet;
4) supplying additional thermal energy at a level above the surface of the carbonaceous material with the aid of a plasma generator;
5) gasifying the carbonaceous material with the oxidant under a pressure exceeding atmospheric pressure to generate the desired gas mixture; and 6) withdrawing the generated gas mixture from the shaft furnace through the said gas outlet;

wherein the thermal energy within the furnace is controlled such that the ash content in the carbonaceous material forms liquid slag which can be tapped off at the bottom of the shaft furnace.

2. The method according to claim 1, in which the oxidant supplied above the surface of the carbonaceous material is sufficient at least partially to oxidize volatile constituents of the carbonaceous material.

3. The method according to claim 1, in which the quantity of H2O, the oxygen-containing gas or CO2 is controlled so as to control the H2/CO ratio in the gas produced.

4. The method according to claim 1, 2 or 3, in which a carbonaceous material in powdered form is injected together with the oxidant at the lower level in the shaft.

5. The method according to claim 1, 2 or 3, in which a material containing Ca and/or Mg in lump form is added together with the carbonaceous material in lump form in order to bind sulphur.

6. The method according to claim 1, 2 or 3, in which the carbonaceous material in powdered form is injected together with the oxidant at the lower level in the shaft, and a powdered material containing Ca and/or Mg is added together with the powdered carbonaceous material in order to bind sulphur.

7. The method according to claim 1, 2 or 3, in which the supply of thermal energy is controlled such that ash content in the carbonaceous material forms a liquid slag which is tapped off at the bottom of the reactor, and a slag-former is added to the carbonaceous material in order to control the melting point and viscosity of the slag.

8. The method according to claim 1, 2 or 3, in which a slag-former is added to the carbonaceous material in order to control the composition of the slag to be suitable for the man-ufacture of cement.

9. The method according to claim 1, 2 or 3, in which the liquid slag is granulated and rapidly cooled with water as it is being tapped off from the bottom of the reactor.

10. The method according to claim 1, 2 or 3, in which the supply of thermal energy is controlled so that ash content in the carbonaceous material remains in solid phase and is fed out as a solid by-product from a bottom part of the reactor.

11. The method according to claim 1, 2 or 3, in which the carbonaceous material consists entirely or partially of coal, coke, pressed coke, wood, partially charred wood, charcoal, lignite or peat.

12. A reactor in the form of a shaft furnace for carrying out the method as claimed in claim 1, comprising (i) sluice arrangement at the top of the shaft for supplying the carbonaceous material in lump form in gas-tight manner to a predetermined filling level in the shaft, (ii) a slag-tapping means arranged at the bottom of the shaft, (iii) an annular drum provided with a gas outlet for withdrawing the produced gas, said annular drum being arranged at a level below the predetermined level to which the solid material is filled, (iv) a plasma generator for supplying thermal energy above the level of the solid material, (v) means for supplying oxidant above the level of the solid material and below the level of the gas outlet, and (vi) means for supplying powdered carbonaceous material below the level of the gas outlet.

13. The reactor according to claim 12, in which the slag-tapping means comprises a rotating feed-out table.