ENK5-2001-00523 Clean Energy Recovery from Biomass Waste & Residues - BIOWARE

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EESD (Energy, Environment and Sustainable Development) : Thermochemical Conversion

Proposal No:	ENK5-2001-00523
Date Prepared:	February 2004
Source:	European Bio-Energy Projects (EUR 20808)

Introduction

Several problems are addressed in this project:

• Stable filtration performance at the operating temperature required for optimal SO₂and NO_x removal is vital for the process of combined dry removal of particles and gaseous pollutants. The critical parameter ranges for filtration must be defined for the fuel's characteristic raw gas concentrations of fly ash and SO₂/HCl (equivalent to sorbent concentrations).
• The development of a rigid SiC based ceramic filter coated with a catalyst for DeNO_x reactions (SCR), dust removal and assessment of the scale up issues of this system.
• The co-firing of biomass materials with coal will generally lead to a reduction in the total fly ash. However, the mixed ash may contain significant levels of very fine aerosol material, which may present problems to conventional particulate emission abatement equipment.
• The effect of the chromium content of the ash from leather wastes on the filtration process and SCR process will be studied, as well the chromium recovery rate.
• The process will result in a production of mixed ashes and sorbent. The utilisation and disposal of the waste material will require careful consideration.

Results

The aim of the filtration study is to define boundary conditions for high-temperature-filtration of fly ash and sorbent mixtures using a dilatometer and a filtration unit (ComFil). The fuels used in the combustion tests were leather wastes and coal/olive oil residue mixtures (60wt% coal and 40wt% olive oil wastes). Flue gas emissions, particulate matter and ash have been characterised on the pilot BFB at CIEMAT. A widely used sorbent for the reduction of hazardous air pollutant (HAP) emissions is sodium bicarbonate (NaHCO₃) and this is to be used in the test work.

Filtration tests of pure NaHCO₃, pure leather ash and mixtures of 75 wt% and 60 wt% NaHCO₃ were performed at 400°C and a back pulse pressure for regeneration of 8 bar. At these conditions the pure leather ash exhibits stable filtration behaviour; on the contrary, the mixture of leather ash with 60 wt% NaHCO₃ at lower pressure of 5 bar showed unstable filtration.

Filtration tests with a mix of fly ashes from olive/coal combustion and NaHCO₃ (30 wt% NaHCO₃) showed to be stable at an operating temperature of 400°C and a tank pressure of 8 bar. According to the preliminary emission values, stable filtration for the fuel leather waste (NaHCO₃ content in the range of 60 to 96 wt% expected) is a problem for operating at temperatures above 300°C. In the case of olive/coal combustion (expected NaHCO₃ content in the range of 15 to 30 wt%) filtration is not a limiting factor.

The operating temperature can be optimised with respect to sorption and SCR reaction efficiencies but should be above the minimum temperature of 240°C (ammonium salt generation). The research work is still going on by optimising the developed catalytic system that already achieves a NO conversion of more than 90 % at filtration velocity of 1cm/s.

Concurrently, a prototype of the experimental facility for use in Soria on the 3.5 MWth BFB has been planned, and the facility is presently under construction. The filtration system consists mainly of the filterhouse and the filter regeneration system. Heating and insulation systems have been designed for thermal conditioning of both the filterhouse and the bypass line (max. 450ºC). Finally, a PLC control system has also been designed in connection with the filtration facility.

The process evaluation has started and the first module of four for the overall techno-economic model has been completed. Once the specifications for the biomass size to the Soria plant have been established, the costs of preparation, drying and the feeding of the biomass or coal/olive oil wastes can be determined. Module III is currently in preparation on gas cleaning to allow for a range of options to be costed and compared. Finally, the activities included in the experimental test in a BFB demonstration plant have been started.

Impact and exploitation

Results of the project include the design and development of a new dry gas cleaning system in a single step. This system is to be optimised for the combustion process, resulting in a prototype capable of operation for a significant length of time.

Once a catalytic filter will be ready for an industrial application, this flue gas system seems very promising as a cleaning system for small biomass combustion plants. Common flue gas cleaning systems of today are too expensive and complex for small and medium size combustion facilities, especially for biomass combustion. Therefore, the application of a catalytic filter may contribute for better local environmental conditions.

Decentralised small biomass plants are a good opportunity for independent energy production. In cases where the fuel is a biomass waste coming from other regional activities, the benefit is doubled: energy is recovered from the biowaste and the waste disposal cost is reduced.

It must be noted that the project results will help to open a new market segment in the field of energy production from biomass combustion. The potential power from leather combustion in Spain and other parts of Europe is estimated to be 150 MWth and 750 MWth respectively. For southern Spain and southern Italy only, the potential thermal power stored in biomass waste from olive oil production can be estimated in the order of 1 GWth and 0.5 GWth respectively.

Furthermore from tanned leather, the resource "chromium III" can be recovered, an element that is not available in the EU and must be imported, mainly from South Africa (66%) and Zimbabwe (29%). A first rough estimate gives a Cr recovery rate of 38 kt/a for European leather industry.