AT500513B1 - Production of hydrogen and usable heat by iron water vapor process comprises gasifying heat low calorific value fuels to raw gas, reducing fuels in reactor and supplying the gas to heat exchangers and water vapor separator - Google Patents

Abstract

After the reduction in the reactor (5), the emerging gas is heated in one or more heat exchangers (8,10) and/or outside the process, the gas is combusted in a weak gas burner to provide a heating source for gasifier (3) and especially water containing low calorific fuel is dried in module (1). After oxidation in reactor (5), the emerging gas is cooled in a heat exchanger with separation of water vapour in separator (12). Reduction is carried out over pellets of iron ore containing additives subjected to subsequent combustion at over 1000[deg]C. The fuel of low calorific value is subjected to air or oxygen enriched air treatment, with removal of dust and then the hydrogen and carbon monoxide containing gas is passed through a reactor (5) at 700-900 (especially 800)[deg]C, and simultaneously through one or more retorts in series or in parallel, and reduced in contact with the pellets of diameter 4-20 mm. In other stages, on contacting with water vapour, a water containing fuel gas is produced.

Description

2 i 2 AT 500 513 B1

The hydrogen production by means of the iron-steam process is carried out by the oxidation of a contact mass, which consists predominantly of iron (Fe) and / or wustite (FeO), with water vapor. The resulting magnetite (Fe304) is reduced by a reducing gas to iron and / or wustite. This process can be operated continuously (e.g., in a fluidized bed) 5 or discontinuously (e.g., in a fixed bed).

A method and system of the aforementioned type is known from patent application EP 0 677 882 A1. In the process known so far, the biomass is first gasified in a reformer with the addition of water vapor or water in a hydrogen-containing raw gas io and then fed to the Rohgasaufbereitungsvorrichtung to produce there the fuel gas. In this known method, the reforming of the biomass is carried out with steam. The raw gas obtained is used as a reducing gas in the metal sponge reactor. A disadvantage of this method is that the raw gas, due to the reforming with water vapor, contains a high proportion of water vapor and thus decreases the Redukti-15 onsfähigkeit the raw gas with respect to the contact mass.

The invention is based on the technical problem of existing methods and systems for the production of hydrogen from contaminated raw gases obtained by the gasification of low-calorific fuels, those having high water contents and / or inorganic contents or high oxygen contents in the organic substance such as biofuel straw, wood, grass, leaves, bark and specially bred, intended for energy use plants, waste such as household waste, industrial waste, municipal and industrial sewage sludge, residues from the processing of used industrial goods, contaminated low-level gases, such as landfill and Clarifying gases and solid / oil or solid / water sludge 25 of different origin can be generated to apply.

This is achieved by gasification with air or oxygen-enriched air, as this way the water vapor content in the raw gas remains low. The reducibility of the contact mass is determined primarily by the partial pressure ratio between hydrogen and water vapor and 30 between carbon monoxide and carbon dioxide. In the case of sponge iron, the limits of reducibility by a raw gas from low-calorific fuels are in the Wüstitstufe.

Since the reduction of the contact mass is many times slower than the oxidation, the reduction is carried out in one or more retorts, which are connected in series or in parallel (FIG. 2).

Since the volume fractions of the fuel gases in the raw gas from the gasification by low-calorific fuels are low, the use of these in the reduction process is low, resulting in further use of the lean gas for heat recovery in and / or outside the process by its combustion and / or use of thermal Energy through heat exchangers or further use outside the process allows.

After reduction of the contact masses, these may be contaminated by deposits of the raw gas 45, for which reason a brief purification step is initiated by steam or another oxidizing agent. This gas is fed to the lean gas stream.

In the following the invention will be explained in two diagrammatic and simplified representations. 1 shows a system of the method according to the invention, which basically has a drying module (1) for low-calorie fuels with a high water content, a gasifier with a dust separator (3), a tar separation (4), a reactor (5), a lean gas further utilization device, consisting of the heat exchangers (8), (10), (15) and (16), the low-gas burners (2) and (9) and the water separator (12), a steam generator module (6) and a fuel gas treatment module, consisting of the gas purification unit 55 unit (7) and the condensation step, consisting of the heat exchangers (11) and (13) and 3 AT 500 513 B1 the water separator (12) includes. Part of the heat gained from the lean gas will continue to be used in the process. The remainder can be dissipated as usable heat at different temperature levels. 5 In detail, the drying module (1) consists of a heat exchanger heated from the outside, this heat is to be seen as the last utilization stage of the lean gas and a continuous fuel delivery, which bring the low-calorific fuels in the carburetor (3), in which they at temperatures between 700 ° C and 900 ° C, preferably at 800 ° C, with the addition of air or oxygen-enriched air io be gasified to a hydrogen and carbon monoxide-containing crude gas, followed by a dust follows and the raw gas in the downstream reactor (5) is oxidized to a weak gas, which is available for further use for the following variants: 15 1. heat dissipation into the system, in particular for heat supply to the gasifier (3) and subsequent to the drying module (1), the possibility of combustion of the lean gas in the Low gas burner (2) is possible. Heat is released from the lean gas stream outside or inside the process via the heat exchanger (8), and the lean gas is subsequently completely burned in a lean gas burner (9), and 20 is used as a heat source for the reactor (5) and thereafter the remaining heat is transferred through the heat exchanger (FIG. 10). 2. The lean gas is reformed by a condensation step, consisting of a condenser (15), a condensate (12) and a superheater (16) in a water vapor 25 me weak gas and the actual raw gas, in whole or in part, mixed. 3. The lean gas, or parts thereof, are introduced into the gasifier (3) directly or after a condensation step as described under point 2. 30

The oxidation step is carried out by means of superheated steam produced in the steam generator < 6). The water vapor is passed through the reduced contact mass obtained from the reduction step into the reactor (5) and forms the fuel gas, which is a water vapor / hydrogen mixture, with simultaneous oxidation of the contact masses. 35

This fuel gas is briefly fed to the lean gas to separate the impurities that have been deposited on the contact masses of the fuel gas stream. Thereafter, the switchover takes place to the fuel gas line. Depending on the requirements of the gas purity, the gas in the gas cleaning unit (7) can be finally cleaned and brought to 40 in the heat exchanger (13) to the required temperature.

The reactor, according to FIG. 2, consists of at least two retorts, at least one of which serves for the reduction and at least one of the oxidation. Since the reduction of the contact mass proceeds much more slowly than the oxidation, it is advantageous to use several 45 retorts for the reduction at the same time. Fig. 2 shows the possible arrangement of three retorts, wherein in a retort (22) the oxidation, and in two series or parallel connected retorts (22), the reduction proceeds. Particularly in the case of retorts connected in series, the partially oxidized raw gas is heated between each retort in a heat exchanger (21), thus ensuring the lowest possible cooling of the contact mass during the reduction. The low-gas 50 recovery (23) takes place afterwards. The energy gained can be used outside and outside the process. 55

Claims (5)

1. A method for generating hydrogen and usable heat according to the principle of the iron-steam process, wherein in a gasifier (3) low-calorific fuels are gasified to 5 raw gas, wherein the raw gas in a reactor (5) the contact mass redu ed and the resulting lean gas in the process and / or used outside the process, wherein in a further step with steam in the reactor fuel gas is generated, characterized in that the low-calorific fuel in the gasifier (3) with dust deposition under supply of Air or oxygen-enriched air is gasified to a io nem hydrogen and carbon monoxide-containing gas, which subsequently in the reactor (5) at a temperature between 700 ° C and 900 ° C, preferably at 800 ° C, simultaneously in one or more retorts connected in series or in parallel, the contact mass is reduced in the form of pellets with a diameter of 4 mm to 20 mm and in a w a hydrogen-containing fuel gas is generated eiteren step with water vapor, wherein: a) after reduction from the reactor (5) emerging gas for heat supply in one or more heat exchangers (8, 10) and / or used outside the process and after combustion in a weak gas burner (2) is used as a heat source for the gasifier (3) and in particular for water-containing low-calorie fuels in the drying module (b), b) the gas leaving the reactor (5) after the oxidation has cooled in the heat exchanger (11 ) is fed to a steam separator (12), and c) pellets are used, which are produced from iron ore with the addition of additives with subsequent firing above 1000 ° C. 25 2. The method according to claim 1, characterized in that the first part of the after the oxidation of the reactor (5) exiting gas, which is contaminated due to deposits on the pellets, is added to the emerging from the reduction gas stream. 30 3 The method of claim 1 or 2, characterized in that the gas emerging from the reduction is used as a heat source for the reactor (5), in particular for re-heating partially oxidized raw gas in the heat exchanger (21) connected in series retorts. 35 4. The method according to any one of claims 1 to 3, characterized in that the reducing gas after cooling in the cooler (15), a steam separator (12) and reheating in the heat exchanger (16) the reactor (5) is supplied again. 5. The method according to any one of claims 1 to 4, characterized in that at heavily contaminated hydrogen and carbon monoxide-containing gases tar separation {4), before the reduction in the reactor (5), takes place. 6. The method according to any one of claims 1 to 5, w characterized in that are used as con tact mass pellets made of hematite powder with additives which serve for reduction reaction acceleration and to increase the strength of the pellets and the stability of the pore system. So for this 2 sheets of drawings 55