Device for online monitoring of alkali-containing gas and aerosol components in hot process gases of a fluidized bed gasification plant and for controlling the addition of an additive

Abstract

Device for online monitoring of alkali-containing gaseous and / or aerosol components in a fluidized bed gasification plant with a recirculation cyclone, characterized in that a high-temperature resistant measuring device is arranged downstream of the recirculation cyclone directly in the hot raw gas stream and is designed for process-true online detection of alkali-containing gas and / or aerosol components in the unconditioned raw gas at process temperatures of at least 300 °C, preferably at about 900 °C, without prior offline sampling and without cooling, dilution or condensation, and that the measuring device is functionally coupled with a control unit which regulates the addition of at least one alkali-binding additive from a reservoir via at least one entry point into the process, wherein the entry point is in particular in the fluidized bed reactor and / or in a recirculation line of the cyclone and / or in a feedstock preparation orPelletizing is arranged, whereby the control or regulating unit controls the additive addition depending on the measured alkali load, in particular on the basis of a threshold value, a temporal trend and / or an alkali load integrated over a time interval, in order to compensate for alkali peaks at an early stage and to reduce deposits / agglomeration / slagging as well as corrosion of downstream plant components.

Description

Technical field The invention relates to a device for online monitoring of alkali-containing gas and / or aerosol components in hot process gases of a fluidized bed gasification plant. The invention relates in particular to a high-temperature resistant measuring device arranged downstream of a recirculation cyclone in a hot raw gas stream and designed for direct measurement without prior sample conditioning, cooling, dilution, or condensation. Furthermore, it is an object of the invention to enable demand-based control of additive addition by means of online monitoring of the alkali load, in order to detect alkali spikes early, avoid agglomerations, slagging, and deposits, and minimize additive consumption. State of the art In the fluidized bed gasification of biomass, waste, alternative fuels (RESH) or sewage sludge, alkali-containing gas species such as KCl, NaCl, KOH, NaOH and alkali-containing aerosols occur in the raw gas. These alkali compounds lead to, among other things: • corrosion and fouling of downstream plant components, • poisoning of catalytic stages, • agglomerations, slagging and deposits, • limited plant availability. Known methods for determining alkali load include: • Offline sampling followed by laboratory analysis, • Measurements after cooling, dilution or condensation of the process gas, • Indirect estimates based on fuel or ash analyses. These methods have significant disadvantages, as they do not provide true online detection, result in a time-delayed reaction, a distortion of the alkali distribution, and an inefficient use of additives. A robust measuring device that directly detects alkali-containing gas and aerosol components in the hot, unconditioned raw gas stream downstream of a recirculation cyclone and uses the measured values ​​directly to control an additive addition is not known in the prior art. Object of the invention The object of the invention is to provide a robust, continuously operating device with which alkali-containing gas and aerosol components in the hot raw gas stream of a fluidized bed gasifier can be measured online, locally, temperature-stable and process-true. Solution to the task The problem is solved by a device according to claim 1. The core of the invention is: • a high-temperature resistant measuring probe, • which projects downstream of a recirculation cyclone into the hot gas stream of a fluidized bed gasifier, • wherein the measurement is carried out at process temperatures of ≥ 300 °C, preferably approx. 900 °C, • and the alkali measurement is performed online, without prior offline sampling The measuring device according to the invention downstream of the recirculation cyclone is not limited to a single measuring method, but is designed as a high-temperature resistant measuring device, which is preferably designed for atomic absorption spectroscopy (AAS) and can alternatively be suitable for other measuring technologies, provided that these enable measurement in the hot, unconditioned raw gas. The measuring device can be designed – as an alternative or supplement to portable atomic absorption spectroscopy – for at least one of the following measurement methods: • Atomic absorption spectroscopy (AAS), in particular portable • Optical emission or absorption methods, e.g., OES, in particular ICP-OES • Laser-based spectroscopic methods • Ion-selective or electrochemical measurement methods • Surface, conductivity, or deposition sensing • Combinations of several measurement principles It is essential that the measurement: • downstream of the recirculation cyclone, • in the hot raw gas at ≥ 300 °C, preferably approx. 900 °C, • is carried out online. The measuring device serves in particular for the online monitoring of the alkali load in the hot process gas and is functionally coupled with a control device for additive addition, which controls the additive addition depending on the measured alkali load, in particular a threshold value, a temporal trend and / or an integrated alkali load. The additives are preferably selected from the group consisting of: • Bentonite, • Kaolin, • other natural or synthetic alkali getters. The additive can be added: • into the fluidized bed reactor, • into the cyclone's return line, • into a pelletizing or feedstock preparation unit, • or at another suitable point in the plant. The combination of downstream measurement in the recirculation cyclone, high-temperature online monitoring of alkali load, and controlled additive addition creates a closed-loop control system that detects alkali spikes early, minimizes additive consumption, minimizes or prevents deposits from agglomeration and slagging, reduces corrosion, and thus increases plant availability. The advantage is that, in practice, the exact quantitative absolute value is less crucial for process control than a reliable qualitative assessment of the alkali status, particularly the detection of spikes, trends, and limit exceedances. This functional overall solution is neither described nor suggested in the prior art. Further advantages, details and features of the invention will also become apparent from the following description and from the drawing 1. This shows in Fig. 1 a simplified carburetor representation with ONLINE monitoring of the alkali load. In Fig. 1, a device for online monitoring (11) of alkali-containing gas and aerosol components in hot process gases (12) of a fluidized bed gasification plant (10) and for controlling an additive addition is schematically shown with (1). The input materials (2), such as biomass, municipal solid waste, shredder light fractions / RESH, sewage sludge, or mixtures thereof, are fed through a shredding unit (5), a grinding unit (6), and a mixing device (7) and subsequently processed in a pelletizing unit (8). The fluidized bed gasifier with recirculation cyclone (10) is fed via a feed system (9). A recirculation cyclone is associated with the fluidized bed gasifier (10); solids separated from the cyclone are returned to the reactor via a recirculation line (13) and a siphon (14). A bottom product is discharged (15). Downstream of the recirculation cyclone, the high-temperature-resistant measuring device for online monitoring (11) is located directly in the hot raw gas stream (12), so that alkali-containing gas and / or aerosol components are detected in the unconditioned raw gas during the process. Furthermore, a reservoir for alkali-binding additives (3) such as bentonite, kaolin, or other alkali getters is provided. Depending on the plant design, the additives can be introduced into the process via alternative entry points (4a-c), in particular into the fluidized bed reactor (10), the return line (13), or into areas of feedstock preparation / pelletization. The measured values ​​from the online monitoring system (11) serve as a control variable for the demand-based regulation of the additive addition from the reservoir (3) via the entry points (4a-c) in order to detect alkali spikes early and reduce deposits or corrosion in downstream plant components. Of course, the examples described can be modified and supplemented in many ways without departing from the basic idea of ​​the invention. Thus, the invention also relates to the process for using additives, such as kaolin, bentonite, or other alkali getters for alkali removal, the fluidized bed gasification of biomass, municipal solid waste, shredder light fractions (RESH), sewage sludge, and mixtures of these components. List of sources 1 Device for online monitoring of alkali-containing gas and aerosol components in hot process gases of a fluidized bed gasification plant and for controlling additive addition. 2 Carbon-containing feedstocks: biomass, municipal solid waste, shredder light fractions (RESH), sewage sludge, and mixtures of these components. 3 Reservoir for additives (bentonite, kaolin, other natural or synthetic alkali getters). 4a, b, c Additive input options. 5 Crushing unit. 6 Grinding unit. 7 Mixing device. 8 Pelletizing unit. 9 Feed system. 10 Fluidized bed gasifier with recirculation cyclone. 11 Online monitoring of alkalis. 12 Raw gas. 13 Recirculation line. 14 Siphon. 15 Soil product.

Claims

Device for online monitoring of alkali-containing gaseous and / or aerosol components in a fluidized bed gasification plant with a recirculation cyclone, characterized in that a high-temperature resistant measuring device is arranged downstream of the recirculation cyclone directly in the hot raw gas stream and is designed for process-true online detection of alkali-containing gas and / or aerosol components in the unconditioned raw gas at process temperatures of at least 300 °C, preferably at about 900 °C, without prior offline sampling and without cooling, dilution or condensation, and that the measuring device is functionally coupled with a control unit which regulates the addition of at least one alkali-binding additive from a reservoir via at least one entry point into the process, wherein the entry point is in particular in the fluidized bed reactor and / or in a recirculation line of the cyclone and / or in a feedstock preparation orPelletizing is arranged, whereby the control or regulating unit controls the additive addition depending on the measured alkali load, in particular on the basis of a threshold value, a temporal trend and / or an alkali load integrated over a time interval, in order to compensate for alkali peaks at an early stage and to reduce deposits / agglomeration / slagging as well as corrosion of downstream plant components. Device according to claim 1, characterized in that the measuring device comprises or is connected to an atomic absorption spectroscopy unit for the determination of sodium and / or potassium compounds. Device according to claim 2, characterized in that the atomic absorption spectroscopy unit is designed as a transportable AAS system. Device according to one of the preceding claims, characterized in that the measuring device is suitable for at least one of the following measuring methods: spectroscopic measuring methods, optical emission or absorption measuring methods, laser-based measuring methods, electrochemical ion-selective measuring methods or combinations of several measuring methods. Device according to one of the preceding claims, characterized in that the measuring device has a high-temperature resistant sampling probe for taking a partial flow of the hot process gas. Device according to claim 5, characterized in that the sampling probe consists of ceramic, metallic or ceramic-metallic high-temperature materials. Device according to one of the preceding claims, characterized in that the control or regulating unit is designed to control the addition of at least one alkali-binding additive. Device according to claim 7, characterized in that the alkali-binding additive is selected from the group consisting of bentonite, kaolin and / or other natural or synthetic alkali getters. Device according to claim 7 or 8, characterized in that the additive is added to the fluidized bed reactor, to a return line of the cyclone, to a feedstock preparation or pelletizing unit or at another suitable location in the plant. Device according to one of the preceding claims, characterized in that the fluidized bed gasification plant is designed for the gasification of biomass, waste (household waste), alternative fuels and / or sewage sludge.

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