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DEMONSTRATION OF A COMMERCIAL SCALE SLAGGING GASIFIER

Objectif

To acquire the performance and operability data to enable slagging gasifiers to be designed and operated to meet predicted engineering and performance guarantees.
Specific project objectives are :
- to obtain product yield and performance data on a range of selected coals;
- to study the influence on performance of feedstocks and operating design variables;
- to establish the effect of scale-up;
- to demonstrate that the slagging gasifier can be operated on bituminous
coals containing a high proportion of fines (up to 50%);
- to demonstrate the long term operability of the gasifier.L%
Phase IIIb. The modifications consisted mainly of converting double off take and hot product gas handling streams into a commercial style single offtake configuration. In the subsequent Phase IIIc. gasification trials, the new system was shown to be entirely successful.
Phase IIIc
(i) Satisfactory operation was achieved at reduced loading with up to 35% fines added to graded mildly caking coal (Markham) and at standard loading with up to 40% fines added to strongly caking coal (Pittsburgh 8). Within these limits, gasifier behaviour was satisfactory for operations with top feed containing as-screened fines.
(ii) Trials with fines agglomerated as pellets produced commercially with a bentonite (cement) binder encountered considerable problems. It was evident that pellet production recipes were coal dependent, and as produced Markham pellets with 25% moisture caused severe handling difficulties. After partial drying, various blends of pellets and lump coal were gasified butthe gasifier behaviour was not considered sufficiently stable for the technique to be adopted.
(iii) Coal/water slurry injection has been demonstrated with coals ranging from highly caking to non caking (Pittsburgh 8, Markham, Illinois 6 and Rawdon). Gasification was satisfactory at an injection rate equivalent to 25% of total feed. It was predicted that the maximum slurry rate would be limited operationally to 30-40% and the technique was limited accordingly to appropriate coals and coal size ranges.
(iv) A programme of pilot plant tests was carried out with various liquid hydrocarbon binders to determine optimum briquette specifications. Gasification trials were carried out with different blends of graded coal and briquettes using pitch or bitumen as binder. Discrete trials were also done for handling comparisons of as-produced and post-fired briquettes and the latter treatment found to be unnecessary. To date 1800 T. of briquettes including Markham and Illinois 6 havebeen gasified and an overall fines content in top feed of 60% was achieved, made up of 50/50 briquettes/lump coal and 10% entrained free fines.
The technique is considered appropriate for general adoption.
(v) It is normal gasifier practise to continuously recycle a portion of the tar produced by the gasifier back to the coal distributor, essentially for the suppression of dust carry-over in the product gas. The main objective of the third Phase IIIc trial was to demonstrate the feasibility of tar reinjection via the tuyeres. The trial was completely successful and showed that tar rates higher than tar production rates were easily achieved.
The practise was adopted as standard for all subsequent trial runs as a means of tar disposal.
Phase V
i) A run of 60 days duration using Markham and Illinois 6 coals successully demonstrated sustained operation of the gasifier.
ii) The gasifier was operated for 40 days spread over 3 runs on strongly caking type 602.
The British Gas Slagging Gasifier programme was initially drawn-up with the objective of meeting British Gas future requirements for coal based substitute natural gas (SNG).
The two principal areas for demonstration were the initial gasification stage and the upgrading of purified gas by methanisation. As there is some uncertainty over the timing of the economic production of SNG fom coal, it is possible that coal gasification may find earlier application for the production of synthesis or fuel gas that can be used in combined cycle power generation plants. British Gas has kept the development programme sufficiently flexible to respond to these wider interests.
THe work was carried out at the Westfield Development Centre, an 18 hectare site orginally commissioned as a Lurgi coal gasification plant to supply town gas at 17. 7 MJ/m3 (475 Btu/ft3).
Of the original 4 Lurgi gasifiers , one was reduced by lining to 1. 8 m. dia and converted to the slagging mode in 1974 and used for thePhase II programme. A second was converted to a 2. 4 m. dia. commercial sized slagging gasifier in 1983 under the Phase IIIa programme and all the others removed.
The programme is in 4 Phases, of which modifications to the gasifier and ancilliaries (Phase IIIb) and conclusion of trials under the revised configuration (Phase IIIc) were both covered by Project LG /00450/85/UK. Actual demonstration of the gasifier was carried out under this contract.
This Phase (IV) is the final one of the programme incorporated experience gained from Phase IIIc, and comprised 2 parts as follows :
Part. 1 A 60 day run to test the gasifier components with net tar production consumed by reinjection and fines addition by the available proven options.
Part. 2 A further 40 days using different ranked power station coals to assess the effects of changes in loading, ash content, and operating flexibility. The fines from the power station coal were made into briquettes and mixed in equal proportions with the lump coal.
- gasifier coal throughput 500T/d;
- oxygen consumption at gasifier design output 270T/d;
- oxygen storage 1,500 T;
- maximum steam consumption 230T/d at 32 Bar, 380 deg. C;
- coal storage capacity 250T. above stockpile;
20,000T. stockpile;
- coal handling capacity 30T/h. maximum into gasifier x 24 h;
- slag handling capacity 276T/d;
- gas cooling capacity 44 Mn3(st)/h.
Gasifier performance was determined from heat and mass balances.

Appel à propositions

Data not available

Régime de financement

DEM - Demonstration contracts

Coordinateur

British Gas plc
Contribution de l’UE
Aucune donnée
Adresse
London Research Station Michael Road
SW6 2AD London
Royaume-Uni

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Coût total
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