DE2035088A1 - Continuous endothermic gasification of dust-using externally - heated tubes with large heat transfer area - Google Patents

Abstract

A continuous flame-free gasification process for dust or fine particles, using steam and/or CO2 with direct external heating of the combustion chamber to 60-1000 degrees C and an operating pressure up to 90 atm., is effected in thin metal tubes, pref. of diam. 80 mm, with turbulent flow. The heat necessary for the endothermic reaction flows radially inwards from the tube wall via relatively large heat transfer surfaces. Specif., a ratio of gasification medium/fuel of 2-5 Nm3/Kg is used.

Description

Method and device for continuous flameless gasification of dusty or fine-grained solid fuels The present invention relates to a method and a device for continuous flameless gasification of dusty or fine-grained solid fuels with steam and / or 002.

The invention is based on the fact that the carbon contained in solid fuels reacts noticeably with the gasifying agents water vapor and / or CO 2 at temperatures above 7000 C according to the following equations: The composition of the gas generated according to the above reaction equations is subject to the known equilibrium conditions of the water gas equilibrium, the Boudouard equilibrium and the methane equilibrium.

In practice these reactions are summarized as gasification are done in different ways.

For example, gasification is operated on a discounted basis Water gas generator known, wherein in the heated coke bed during the blowing period Steam and / or C02 is blown in until, as a result of the heat release of the coke, the temperature in the coke bed drops so much that the gasification freezes, followed by a new blowing period.

It is also the use of a continuously operated generator known, in which the coke bed located therein by applying an electrical Voltage that acts as resistance heating to the required reaction temE> erattar is heated.

It is also proposed in German Patent 530 064 The gasification of fine-grained or powdery solid fuels to be carried out in a large chamber, the necessary for the gasification Heat supplied from the outside via heating channels located inside the chamber lining will.

German patent 531 208 also relates to gasification of fine-grained or dusty solid fuels in an externally heated Decomposition chamber. To improve the Heat transfer and des Degree of conversion of the gasification is provided that the fuel dust and the water vapor are blown into the decomposition chamber in such a way that they enter it circle. There are also special built-in components in the decomposition chamber for this purpose intended.

The gasification in an externally heated displacement chamber can in principle entail a number of advantages, which are discussed further below should be received. Despite these advantages, the way of working that is implemented in the last mentioned German patents is described in practice do not know how to enforce. This is mainly due to the fact that the Heat transfer from the heated wall of the decomposition chamber to the fuel particles As a result of the tammer construction used and the chamber dimensions used so far is insufficient and uneven. That in turn has an incomplete gassing result. This disadvantage could not be overcome by installing special circulation devices be encountered within the decomposition chamber. Furthermore, it has a disadvantageous effect from that the establishment of such large chambers with not inconsiderable costs connected is.

The invention was therefore based on the object of the process for continuous flameless gasification of dust-shaped or fine-grain solid fuels in externally heated decomposition chambers so improve that the Disadvantages resulting from the prior art can be avoided and thus the special advantages of this way of working can come into their own.

This goal is achieved by a process for continuous flameless gasification of powdery or fine-grained solid fuels with Steam and / or G02 in reaction rooms heated directly from the outside at temperatures between 600 and 10000 C and pressures up to 90 atmospheres, which is characterized by that the gasification is carried out in metal pipes with an inside diameter that is not too large in which there is a turbulent flow and that the reactants the heat required for the endothermic gasification reactions uniformly radially from the pipe walls by relatively large in relation to the volume flowing through Heat exchange surfaces is supplied.

The invention is based on the consideration that the required Heat for the gasification as quickly and evenly as possible to the reactants This can be achieved by: 1.) Relatively large heat exchange surfaces in relation to the volume flowing through, 2.) short distances from the Heat exchange surfaces for the fuel to be gasified and 3.) turbulent flow within the reaction space, so that the individual fuel particles repeatedly come into contact with the gasification agent.

These conditions are best met by those provided by the present invention Metal pipes met. The clear diameter of these tubes should preferably be do not exceed 80 mm. In order to increase the heat exchange surfaces can the tubes may also be provided with ribs.

The method according to the invention is described below using the method described in FIG Figure reproduced flow diagrams are explained in more detail.

The fuel to be forgotten becomes dusty or fine-grained, that is with a very large active surface, from the pressure vessels 1 via a shut-off valve 2 and adjustable locks 3 in the highly heated fermentation medium (steam and / or C02).

Ee at least 2 pressure vessels are provided in each case, so that the injection of the fuel dust can be carried out continuously in the gasification agent.

The gasifier / fuel ratio can be adjusted and adjusted depending on the purpose of the gas produced and the properties of the respective Fuel. The ratio is in the order of about 2 - 5 Nm3 gasifying agent / kg of fuel.

The mixture of gasifying agent and fuel now passes through External heating to approx. 10000 C heated Netali tubes 4.

In these there is now a rapid heating of the mixture to the Reaction temperature. The metal pipes are empty, i. H. they only contain what has been given up Mixture of gasifying agent and fuel as well as the gas already generated.

In the metal pipes, the gasification of the fuel now starts according to the equations (a to t).

When the fuel is injected into the hot gasification agent degassing occurs with fuels that have a low degree of coalification. This degassing, however, is due to the onset of gasification in the metal pipes interrupted, and already formed degassing products are split up.

When flowing through the metal pipes 4, the fuel given gas is gasified and what remains is the ashes. Since the gasification temperature is in the In the range of 600 - 10000 C, there is no melting of the ash and thus no slag formation. The powdery ash is therefore generated with the Gas discharged. In a downstream device, e.g. B. multicyclone and electrostatic precipitator, which is arranged at a suitable point in the process sequence can contain the ashes be deposited from the gas.

The individual metal pipes are combined in a common rammer 5. This chamber 5 is thereby heated several burners 6 directly. The heating takes place so that each metal tube 4 is supplied with approximately the same amount of heat.

The burners can be arranged in the chamber ceiling or in the side walls.

The figure shows that the burners are in the chamber ceiling are arranged and that the heating takes place with coal dust.

This coal dust comes from the bunker 7 via the valve 8 and the Distribution base 9 to the burner 6. The necessary combustion air is supplied with the fan 10 promoted to burner 6.

The flue gas generated in the burners 6 heats the metal pipes 4 and leaves the furnace chamber 5 at a temperature of about 10,000 c.

The sensible heat of the flue gas is used in a preheating group 11, z. B. to preheat process steam and boiler feed water. Then will the flue gas is blown into the atmosphere via the fan 12.

The gas generated in the metal pipes 4 is fed to a manifold. It is then cooled in'dem waste heat boiler 14.

When cooling, steam is generated in an amount that is well enough for the gasification of the abandoned fuel.

Behind the waste heat boiler 14 you can use the gas by direct or indirect Cool down further and then dedust.

However, it can also be done behind the waste heat boiler 14 at one temperature from approx. 320 - 3800 C in an appropriate facility (multi-cyclone / E-filter) dedusting if the gas treatment process requires it, e.g. B. if a downstream CO conversion is provided.

The following is the result of a profitability calculation for the inventive method for the flameless gasification of coal dust with Steam can be reproduced with the production of raw synthesis gas containing CO + H2.

When using 480 kg of coal dust with the following composition: Water 1.70 wt% ash 27.52 "C 59.32" H 3.39 "s 0.92 N 1.38" O 5.77 "100.00 % By weight approx. 1250 Nm) gas with the following composition: CO2 18.00 % By volume CO 18.30 "H2 61.27" N2 0.40 "CH4 1.80" H2S 0.23 "100.00% by volume therein approx. 1000 Nm³ CO + H2 as useful gas portion.

Here, a ratio of water vapor to carbon in the coal dust was established of 4.0: 1 applied.

Approx. 1,300,000 kcal are required to heat the metal pipes or expressed in coal dust approx. 235 kg.

If you get from the same coal dust by partial oxidation in one Dust gasifiers suitable for this also generate 1000 Nm3 Co + H2 in the raw synthesis gas want, then approx.

730 kg of coal dust required. The gas generated here has the following Composition: CO2 11.8% by volume CO 56.3 H2 30.1 N2 + Ar 1.4 "CH4 0.1 H2S 0.3" 100.0 vol .-% A comparison of the two processes is as follows from flameless Dust gasification water vapor through partial gasification oxidation coal dust for gasification kg 480 730 coal dust for heating kg 235 coal dust in total kg 715 730 oxygen for gasification Nm3 - 410 CO + H2 in the raw gas Nm3 1000 1000 The above list shows that with dust gasification by partial oxidation for the production of 1000 Nm3 CO + H2 in the raw gas incur additional costs for the required oxygen.

At an oxygen price of DM 5, - per 100 Nm3 ° 2, the costs are DM 20.50 per 1,000 Nm3 CO + H2. If from the CO + H2-containing raw gas z. B. NH3 generated should be, the additional costs for oxygen, taking into account, that per t N113 2200 Nm3 CO + H2 are required, DM 45.00 per t NH3.

The above profitability calculation clearly shows the advantages recognize the continuous flameless gasification.

It should also be taken into account that the investment costs for Processes according to the invention are lower than in the older processes according to the German patents 530 064 and 531 208. The method according to the invention draws In addition, compared to these processes, the degree of implementation is significantly improved and increased operational reliability.

Claims (5)

Claims Process for the continuous flameless gasification of dusty or fine-grain solid fuels with water vapor and / or CO2 in from the outside directly heated reaction spaces at temperatures between 600 and 10,000 C and pressures up to 90 atmospheres, characterized in that the gasification in metal pipes with no too-large clear diameter is carried out in which a turbulent flow prevails, and that the reactants are responsible for the endothermic gasification reactions required heat evenly radially from the pipe walls through in proportion relatively large heat exchange surfaces are supplied to the volume flowing through. 2.) The method according to claim 1, characterized in that the gasification is preferably carried out in metal pipes, the clear diameter of which is the value does not exceed 80 mm. 3.) Process according to claims 1 and 2, characterized in that that the gasification is carried out in Netali tubes for the purpose of increasing the heat exchange surfaces are ribbed. 4.) Process according to claims 1 to 3, characterized in that that in gasification a ratio of gasifier to fuel in the range of 2 - 5 Nm3 gasifying agent per kg fuel is adhered to. 5.) Device for performing the method according to the claims 1 to 4, characterized in that several metal pipes (4) together with the for direct heating serving burners (6) zueammengefasst in a common chamber (5) and that a preheating group (11) is also arranged in the chamber (5). L e r s e i t e