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REGENERATIVE DESULPHURIZATION IN FLUIDIZED BED COMBUSTION OF COAL

Objective

THE PROJECT IS PROPOSED TO INVESTIGATE IF CERTAIN ALKALINE SORBENTS CAN ABSORB SULPHURDIOXIDE IN SUCH A WAY THAT ECONOMIC OPERATION OF A COAL COMBUSTOR TO RAISE ENERGY IS POSSIBLE WITH AT THE SAME TIME REDUCTION OF THE ENVIRONMENTAL PROBLEMS. IT IS EXPECTED THAT A REGENERATION SORBENT CAN BE DEVELOPED WHICH IS SUITABLE FOR THIS PURPOSE.

THE RESULTS WILL FILL A GAP IN THE STATE OF THE ART, WHERE IT IS KNOWN THAT SORBENTS CAN CAPTURE SULPHURDIOXIDE BUT UNKNOWN IF THERE ARE SORBENTS WHICH BE REGENERATED IN AN INDUSTRIAL PROCESS. THIS IS THE MORE SERIOUS BECAUSE IT IS LIKELY THAT RAISING THE PRESSURE IN THE COMBUSTOR HAS SEVERAL TECHNICAL ADVANTAGES, MAINLY AS TO THE ENERGY EFFICIENCY BUT THERE IS NOT MUCH EXPERIENCE, CERTAINLY NOT IF SULPHURDIOXIDE SHOULD BE CAPTURED IN SITU.
THE EXPECTED RESULTS CAN BE APPLIED BY THE PRODUCERS OF POWER AND ELECTRICITY I.E. INDUSTRY AND UTILITIES.
A new calcium oxide on gamma aluminium oxide (AL2 03) sorbent has been developed as a more economic sorbent for regenerative desulphurization. Its properties ensure relatively fast sulphation, selective and fast regeneration and good attrition resistance. A model for segregation in slugging fluidized beds is proposed from which can be calculated the conditions required either to avoid segregation or to provoke it. Engineering sulphur retention (SURE) models are built on the assumption of ideal mixing and on models for sorbent sulphation.

The feasibility of the sulphur retention with sol gel sorbent is demonstrated technologically in a pilot scale pressurized fluidized bed combustion (FBC) test. Its economic feasibility is tested using 2 different economic models, but the advantages are dependent on whether or not spent sorbent contaminated with coal ash is regarded as chemically hazardous waste.
IN THE CURRENT POLICY TO EXTEND THE RAW MATERIAL BASIS FOR ENERGY PRODUCTION, A LARGE CONTRIBUTION FOR THE FUTURE IS EXPECTED FROM THE USE OF COAL. IN THE DIRECT ENERGY PRODUCTION BY COMBUSTION OF COAL IT IS REALIZED, HOWEVER, THAT IMPURITIES IN COAL MAY BE A NUISANCE TO THE ENVIRONMENT. ESPECIALLY SULPHURDIOXIDE GENERATED BY COMBUSTION DRAWS ATTENTION AS A PRECURSOR OF "ACID RAIN". METHODS HAVE BEEN DEVELOPED TO PURIFY STACKS GASES OR TO REDUCE THE SULPHURDIOXIDE EMISSION BY ADDING SULPHUR CAPTURING SORBENTS TO THE COMBUSTION FURNACES.

HOWEVER, SULPHUR CAPTURED IN THESE METHODS WILL GENERALLY LEAD TO A SHIFT OF THE PROBLEM AND NOT TO A REAL SOLUTION. IN THE CASE OF SULPHUR CAPTURING SORBENTS IN A FURNACE A SOLID SULPHATE IS FORMED E.G. CALCIUMSULPHATE (GYPSUM) WHICH HAS TO BE DISPOSED OF. THE GOVERNMENTAL POSITION PAPER ON COAL TO THE PARLIAMENT IN THE NETHERLANDS GIVES A FIGURE OF 2 MILLION TONS OF SULPHATE PER YEAR, WHICH NATURALLY WILL BE BURDEN TO THE WASTE DISPOSAL POLICY.

THE OBJECTIVES OF THE UNDERLYING PROPOSAL ARE TO DEVELOP A METHOD WITH WHICH A SORBENT LOADED WITH SULPHATE CAN BE REGENERATED AND RECYCLED. DURING THE REGENERATION SULPHURDIOXIDE IS RELEASED IN SUCH A CONCENTRATION THAT IT CAN BE EXTRACTED IN AN ECONOMIC WAY. THE REGENERATION AND RECYCLE PROCESS WILL NOT BE AN ETERNAL ONE. THERE WILL BE A CERTAIN LIFETIME OF THE SORBENTS. HOWEVER, THE AMOUNT OF SOLID WASTE IS REDUCED REMARKABLY.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

TECHNISCHE UNIVERSITEIT DELFT
Address
Julianalaan 134
2628 BL Delft
Netherlands

Participants (1)

TWENTE UNIVERSITY OF TECHNOLOGY
Netherlands
Address

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