Prospects for use of PDP pour-depressant additive in diesel fuels

Abstract

Pour depressants began to be used in diesel fuels in other countries in the 1970s, even though they did not lower the cloud point. The domestically manufactured additive PDP, which is produced at the Naftan Production Association (Novopolotsk, in Belarus) is a universal additive, it is effective in both summer- and winter-grade diesel fuels [3, 4], as illustrated by the comparative data of Table 1. Here, the effectiveness of the additives was rated by means of laboratory determinations of the cloud point t c, solid point t s, and limiting filterability temperature tf of diesel fuels with and without the PDP additive. As can be seen from these data, the PDP additive is very effective, especially in winter-grade fuel. It even depresses the cloud point -- an effect that is generally not given by imported additives. The results from evaluations of low-temperature properties of diesel fuels by standard laboratory methods do not always give a correct prediction of fuel behavior in actual service. Therefore, let us examine the results from tests on the summergrade fuel L-0.5-40 (GOST 305-82) from various batches, blended with the PDP additive, in test stands at NAMI [Central Scientific-Research Automotive and Engine Institute] and VNII NP [All-Russian Scientific-Research institute for Petroleum Processing], and also in facilities located in the Urals and West Siberia where automotive and tractor equipment was operated during the winter periods of 1991 to 1993. The effect of the PDP additive on the starting properties of the KamAZ-740 automotive diesel was investigated in the climate chamber of NAMI, using two additive-blended diesel fuels: summer-grade L-0.5-40 plus additive, blended at the test site; winter-grade DZp-0.5 (specification TU 38.101889-81), prepared at the Naftan Production Association by blending summer-grade fuel with the PDP additive. Comparison tests were run in the same engine on fuels without additive: summergrade l;ael L-0.5-40 and winter-grade fuel "Z minus 35" (GOST 305 - 82). All of these fuels were further evaluated in a Sever2 test unit at VNII NP by an interdepartmental method for determination of the limiting filterability temperature (filtration through a BT-170 paper filter) and the fuel pumpability (through an FGO coarse filter) under engine-starting conditions. As can be seen from the results of these tests (Table 2), the addition of 0.1% (wt.) of the PDP additive to the summergrade diesel fuel lowered t s by 25 ~ and improved the low-temperature capability of the diesel feed system by~ 12~ this latter result matched the rating of operational effectiveness of the filtration system in the Sever-2 unit (13~ Both samples of the summer-grade fuel with the PDP gave reliable operation of the feed system and satisfactory starting of the engine at -25~