Gas scrubber for offal processing and biodigesters
Introduction to Ravebo and its Wet Scrubber Systems
Ravebo is a leading manufacturer of wet scrubber systems and installations for reduction of harmful and odour loaded gas emissions in the industry.
Gas Scrubbing for Biogas Industry
The biogas industry intends to generate energy from biogas from manure. The processing of the manure will lead to undesirable odour emission to the environment and must therefore be reduced with a gas washing installation. For one of these companies Ravebo has developed such an installation. The organic waste is brought to the biogas plant and then sent on to the plant’s processing tanks (digesters). In the digester bacteria convert biomasses into biogas and liquid fertiliser (digestate).
Cleaning Sequence of Scrubbers for Gas Emission Reduction
The exact gas composition and the associated odour load is not known at this time. Based on our experience, it is to be expected that several components will be present in the gas after manure fermentation. This includes amongst other things NH3, H2S, DMS, Monochloramines, Thiazoles, and fatty components. The proportions between the different components are not known as also the concentrations of the components or fatty particles. Based on our experience, we know that the gaseous components will prevail and, with their characteristic low odour thresholds, will cause the biggest emission problems. Ravebo has decided to opt for the cleaning sequence of the scrubbers as described. However, it should be noted that the sequence can be adjusted, and the sections also can be interchanged relatively easily.
Scrubber Operation and Control
The scrubber operates according to a so-called closed loop system with KSB pumps in which the washing sections consist of open spray basics. The scrubber has retractable spray lances equipped with tangential spray nozzles which generate a homogeneous spray pattern with ultra-fine droplets for an optimal absorbing process.
The scrubber installation is controlled using a Siemens S7-1500 PLC with HMI-screen which is built-in a Rittal cabinet where the electrical components are mounted.
Continuous Washing Liquid Measurement and Dosing of Chemicals
The washing liquid level is continuously measured in each integrated buffer using Endress+Hauser level switches for the operational and alarm levels. The discharge of washing liquid depends on the conductivity level. The fresh water supply is based on the liquid level.
A system for measuring the pH value and/or free chlorine value for dosage purposes is added for the control of chemicals, the signals are processed using a controller which is built into the control cabinet.
The dosing of the sulphuric acid, sodium hypochlorite and caustic soda of the relevant washing section is done via flexible dosing pipes. The Iwaki dosing pumps are directed on the measured pH and free chlorine values, based on these values, the correct amount of caustic soda, sodium hypochlorite or sulphuric acid is automatically dosed.