DE20020240U1 - Waste gasifier - Google Patents

Description

Waste gasifier

The invention relates to the field of environmentally relevant waste disposal by means of fixed bed pressure gasifiers, wherein the waste materials used are primarily solid carbon-containing waste materials which have varying proportions of thermoplastics.

Fixed bed pressure gasifiers were developed and operated for the extraction of gas from coal. For this reason, all components of a fixed bed pressure gasifier have been optimized for maximum gas yield. At the beginning of the 1990s, solid carbon-containing waste materials, including those with thermoplastic components, were started to be gasified in these fixed bed pressure gasifiers. It turned out that the coal distribution devices in the upper part of the fixed bed pressure gasifier, known from coal gasification, were not suitable for the use of solid carbon-containing waste materials, since most of these waste materials are a mixture of materials that react thermally very differently and the proportion of thermoplastics fluctuates and cannot be predicted from the outset.

The high-performance coal distributor known from brown coal gasification and proven there resembled a truncated cone-shaped roof with an angle of inclination of approx. 50°, on which a hollow cylinder open at the bottom with a raw gas outlet on the side was placed. The cavity under the truncated cone-shaped roof, together with the attached hollow cylinder, served as a gas collection chamber. This combination of coal distributor, gas collection chamber and raw gas outlet intentionally created an annular gap between this assembly, which was arranged in the middle of the upper part of the fixed bed pressure gasifier, and the inner wall of the generator, for the supply and distribution of the introduced brown coal briquettes to the bed. This design is roughly described in the specialist book: Gaserzeugung und Gasaufbereitung, Publisher: Gaskombinat Schwarze Pumpe, Deutscher Verlag für Grundstoffindustrie Leipzig 1987, page 202. A schematic representation of the assembly described above can also be found in DE 41 25 518.

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The structural combination of coal distributor, gas collection chamber and raw gas outlet mentioned above has proven itself in the gasification of brown coal briquettes. The described design of coal distributor and raw gas outlet has proven to be unsuitable for the use of waste materials with thermoplastic plastic components - and this is the majority of the types of waste available on the market. When using the solid carbon-containing waste materials mentioned above with thermoplastic plastic components, the plastic phase of the thermoplastic plastic component occurs in accordance with the temperature distribution in the fixed bed pressure gasifier, well into the upper part of the fixed bed pressure gasifier, still at the level of the so-called coal distributor. The plastic part of the waste materials used sticks to the surface of the truncated cone-shaped roof of the coal distributor and thus reduces the opening width of the annular gap between the coal distributor and the generator inner wall, which is essential for optimal filling of the fixed bed pressure gasifier. In extreme cases, this annular gap can be completely closed. In the latter case, this requires the fixed bed pressure gasifier to be shut down immediately. Bonding without complete closure of the annular gap leads to poor generator filling, resulting in poor raw gas quality, increased dust discharge from the fixed bed pressure gasifier, risk of oxygen breakthrough and increased cleaning effort.

The coal distributor known from the gasification of lignite briquettes is therefore not suitable for the use of carbon-containing solid waste, especially those containing thermoplastic components.

The problem underlying the invention is therefore to find a technical solution with the help of which solid carbon-containing waste materials, in particular those with thermoplastic components, can be easily fed and gasified in conventional fixed-bed pressure gasification plants.

The problem is solved by placing a cylindrical or conical chute below the lower closure head of the feed lock, which extends approximately 700 to 1200 mm into the fixed bed pressure gasifier. Its diameter depends on the design of the fixed bed pressure gasifier. This chute is uncooled, but is made of thermostable material.

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The temperature distribution in the fixed bed pressure gasifier is such that the so-called pyrolysis zone with temperatures between 575 - 700 ⁰ C is already located below the hopper. A hollow space is inevitably created to the side of the hopper as a gas collection and settling chamber. In this gas collection and settling chamber, a pipe bend or a pipe corner piece extends up into the dome area of the fixed bed pressure gasifier. Pipe bends or pipe corner pieces can be closed off at the top with a T-piece that is attached to minimize the gas velocity.

The solution according to the invention is characterized by the following advantages:

- Complicated installations can largely be dispensed with.

- A uniform filling is achieved in the fixed bed pressure gasifier.

- The entire filling surface can be used as a gas outlet surface, which reduces gas velocity and dust discharge.

- The central gasification material feed greatly reduces the safety risk of an increase in oxygen in the raw gas, since a fixed bed pressure gasifier tends to be so-called centrally located, independent of the discharge devices.

- The larger free space above the fuel bed ensures safe pyrolysis of the waste materials containing thermoplastic components.

- Due to the inventive arrangement of the chute and raw gas discharge, the gasification material loading height is approx. 1.5 - 2 m higher than with the original design of the coal distributor. This ensures a higher carbon supply in the fixed bed pressure gasifier and at the same time ensures space for the loss of mass of the gasification material fed in due to pyrolysis at high admixture rates of waste materials with thermoplastic properties, without increasing the risk potential.

The invention will be briefly explained below using an embodiment. The associated figures 1 and 2 show a conical and a cylindrical chute. The embodiment relates to the arrangement according to figure 2.

A cylindrical hopper 1 is arranged centrally below the lower closure head of the feed lock 5. This hopper extends approximately 1000 mm into the fixed bed pressure gasifier. The open diameter of the hopper 1 is 1450 mm. The distance between the bottom of the hopper 1 and the hopper surface 4 is a minimum of 500 mm, depending on the operating mode.

The raw gas discharge 2 consists of a pipe corner piece which extends up into the dome area of the fixed bed pressure gasifier 3 at the side next to the chute 1 and which has a T-piece arranged above the opening of the raw gas discharge in order to minimize the gas outlet velocity.

Claims (3)

1. Waste gasifier which operates according to the principle of fixed bed pressure gasification and is fed with solid carbonaceous waste materials which contain a varying proportion of thermoplastics, characterized in that a conical or cylindrical chute is arranged in the dome of the fixed bed pressure gasifier centrally below the lower closure head of the feed lock, which extends approximately 700 - 1200 mm into the fixed bed pressure gasifier, and that further to the side of this chute a raw gas discharge is arranged which consists of a pipe corner piece or a pipe bend which are led into the dome area of the fixed bed pressure gasifier. 2. Waste gasifier according to claim 1, characterized in that the chute is uncooled and consists of thermostable material. 3. Waste gasifier according to claim 1 and 2, characterized in that the pipe corner piece or the pipe bend can have a T-piece placed over their gas inlet opening.