HYDROPYROLYSIS OF COAL

Objective

To study hydropyrolysis of coal in an existing open loop pilot plant to be equipped with :
- 1) a methane reforming reactor;
- 2) a gas recycling purification loop;
- 3) a sand/char recycling-separation device.L%
A. Design of the gas recycling loop
The loop includes a PSA rig to separate hydrogen from other gases, a shift reaction, a decarbonatation-desulfurization with M. D. E. A. solution, a H2S-guard with ZnO, and a methane reforming reactor using oxygen.
The loop is now designed to handle the entire flow rate leaving the reactor, in opposition to the initial proposition where only a fraction of the gas was treated.
Nevertheless, the loop will remain open as foreseen previously. It will be cut between the ZnO vessel and the reforming reactor.
The build-up of the recycling loop is presently finished. Electrical works and start-up phases have begun.
B. Sand-char separation
The conclusions can be summarized as follows :
. The continuous separation gives similar results as the batch separation, provided that the bed has dimensions adapted to the solid flow rate.
. This technique, separating sand from char, can thoroughly be used at ambient temperature and atmospheric pressure.
. The thermalbalance of the hypy reactor shows that the calorific profit due to a separator recycling hot sand at reactor pressure exists only above a minimum coal flow rate.
. However the control of the sand circulation in the conditions prevailing in the hypy reactor appears little reliable.
Consequently, the on-line segregation is not the way which would be used in an industrial plant.
C. New design of the reactor outlet and of its sand feeding
A modification of the reactor outlet and of its binding to the char cooler has been studied, in order to eliminate narrowings and elbows with too short radius. Small char crusher is inserted between the reactor outlet and the char cooler inlet.
Moreover, a new separate sand feeding system was designed.
This project is but one Phase in a larger hydropyrolysis programme and represents a complementary development towards the demonstration of an existing open loop pilot plant for coal hydropyrolysis. The plant was built and operated with the assistance of financial aid from the Belgian government.
The plant operates at 850 deg. C, up to 50 bar and handles coal at 100 kg/h. The coal, when ground and screened, is in some cases mixed with an inert silicious sand. This is continuously fed into a pressurised entrained bed reactor in which pyrolysis occurs and free radicals formed react with hot 80 % hydrogen gas.
1. The design of the recycling loop must ensure a sufficient hydrogen production in order to keep up a sufficient hydrogen partial pressure, with regard to hydrogen consumption and gases generation. Methane reforming and char gasification have been considered and compared as possible means to create the required hydrogen.
2. To avoid risk of accumulation in the loop of gases created in the reactor, the gas recycled is selectively cleaned: CO2, CO, CH4 and H2S are the gases which are primarily extracted. The recycling loop will therefore include a shift reaction vessel, and devices to separate H2 from CH4 and CO2. Additionally, H2S in the recycled gas must be completely eliminated to avoid problems associated with high temperature corrosion.
The dry desulphurisation system using MnO on Al2O3 as absorbent has been considered and compared with the wet desulphurisation with M.D.E.A.
The wet process has finally been prefered.
3. When sand is added to the coal, one separation possibility being considered is the segregation by fluidization, where dense particles tend to sink through the fluidised bed and lighter ones rising to the top. This infers that at low gas velocity lighter char will float on top of the sand bed in "quasi" separation. The collecting port on top of the bed should take only char and the bottom situated port, only sand.
A three-point study was foreseen in relation to continuous recycling of the char/sand mixture in the reactor, viz : - the amenability of the char/sand mixture as it leaves the hypy reactor to be separated by fluidization,
- the design of a continuous separator operating at ambient temperature and atmospheric pressure,
- the influence of pressure and temperature on segregation efficiency on a separator operating at hydropyrolysis conditions, and means to control the phenomenons and flow rates.
The project was scheduled for completion in five phases, beginning May 1987, ending December 1991. Phases 1, 2 and 3 which include char/sand separation and solid recycling loop; gas recycling loop and H2 generation respectively, will run in parallel with orientation tests relative to phases 4 and 5 (measurement and optimisation of operational variables (experimentally) and flexibility in comparison with coal). Total cost of the work to be carried out at INIEX is 2,241,605 ECU.

Programme(s)

ENG-ENDEMO C - Programme (EEC) of demonstration projects and industrial pilot projects (EEC) in the energy field, 1985-1989

Topic(s)

6.2 - LIQUEFACTION

Call for proposal

Data not available

Funding Scheme

DEM - Demonstration contracts

Coordinator

INST. NATIONAL DES INDUSTRIES EXTRACTIVES (INIEX

EU contribution

No data

Address

RUE DU CHERA 200
4000 Liege
Belgium

Total cost