After installation and test-running of the two first gasifiers, some problems with the presence of tar in the scrubbers, filters and engines occurred. Very high temperatures in the gasifiers were also registered. These abnormalities or difficulties were not observed, when the equipment was tested in Germany before delivery to Paraguay. The reasons for this were expected to lie in the fact, that during the test-runs in Germany the wood fuel used was a local pine while the wood-fuel in Chaco was of Quebracho blanco origin.
As a first measure the two wood-fuels under question were analyzed in more detail, and the results indicated following facts:
1 The tar and ash contents of the Quebracho-wood were twice as high as the respective values for the German pine.
2. The heat value of the Quebracho wood was also higher.
To solve the above-mentioned problems with tar contamination an extra air-injection device, as shown in figure 6.3, was installed in the gasifier, and an extra secondary charcoal filter was taken into use. To be able to lower the temperatures in the reactor the gas volume had to be decreased by 30%. This of course had a negative influence on the gasifier capacity. In the design of the third gasifier unit, these experiences were taken into account and resulted in a somewhat modified outfit, as mentioned in Section 6.3. In 1985 the gasifiers have worked more or less trouble-free and the maintenance and repair costs have decreased by roughly 40%. (9)