Catalysis 2024 Issue

Test results of vacuum dryer simulation study

Sr. No

Experiment

Feed moisture, Residence time,

Temp.,

Vacuum,

Product visual Product moisture

wtppm

minute 2 min 3 min 5 min 2 min 2 min 2 min 2 min 10 min

ºC

torr 100 100 100 100 100 100 100 100 100

appearance

ppm 115 102

At different residence time

177

100 100 100 100 100 105 110 115 100 100 100 100

Hazy

Slightly hazy

Clear Clear Hazy Clear Clear Hazy Clear Clear

90 91 95 76 78 97 88 82

At different temp.

180

107

Slightly hazy

At different vacuum level

160

2 min 2 min 2 min 2 min

105

95 90 85

Slightly hazy

Table 1

The dryer is operated in batches and can control and study the effect of vacuum, temperature, and residence time.  Diesel sample: Since the product diesel sample was not showing enough haziness for study, the techno vacuum dryer inlet samples were collected from the DHDS unit for Aim: To analyse moisture and haziness of dryer inlet samples. Exp. conditions: The dryer inlet samples were collected from the DHDS unit on different dates and cooled to room tem- perature. They were then tested for moisture by ISO 12937 and appearance by ASTM D4176, P-1 (haziness visually). Observations: The dryer inlet diesel samples were always hazy, and moisture content varied widely between 172 and 591 wtppm. The test results were as expected.  Experiment 2, Simulation study of vacuum dryer: vacuum dryer simulation study at the laboratory.  Experiment 1, Analysis of dryer inlet sample: Aim: To simulate the vacuum dryer operation and study the effect of vacuum, temperature, and residence time on mois- ture content and haziness of diesel sample. The test results of this experiment are useful to identify whether haziness is due to moisture or surfactant molecules. Also, having access to operational parameters will be beneficial in order to opti - mise the performance of the techno vacuum dryer. Exp. conditions: For this experimental work, hazy diesel

samples from the dryer inlet were used for the simulation study, and experiments were conducted using different con- ditions of vacuum level, temperature, and residence time. The experimental conditions and test results after sample cooling to room temperature are listed in Table 1 . Figure 2 shows the feed and product samples of the simulation study. Observations: • Experiment Sr. No.1 was conducted with various res- idence times at a constant temperature and vacuum level. The test results of change in residence time indicate that moisture content is reduced upon increased residence time and haziness is improved. The haziness cleared at more than five minutes’ residence time with 100 torr vacuum and 100°C temperature. • Experiment Sr. No.2 was conducted at various temper- atures with constant residence time and vacuum level. The test results of change in temperature indicate that, upon temperature increase, moisture content is reduced and haz- iness is improved. The haziness cleared at more than 105°C temperature with 100 torr vacuum and two minutes’ resi - dence time. • Experiment Sr. No.3 was conducted with various vac- uum levels, constant temperature, and residence time. The test results of change in vacuum level indicate that, upon increased vacuum level, moisture content is reduced and haz- iness is improved. The haziness cleared at less than 90 torr with 100°C temperature and two minutes’ residence time. • Experiments Sr. No.1, 2, and 3 confirm that haziness in diesel study samples is due to free water molecules. Theoretically, if surfactant molecules are present, the hazi- ness of the diesel sample may not clear by changing these physical parameters. Measurement of haziness Aim: To analyse appearance by different test methods. Exp. conditions: As per ULSD product specifications, die - sel product is tested for appearance per ASTM D4176, P-1 (visual examination of fuel clarity). As per ASTM method terminology, clear and bright (CB) means a condition in which the liquid fuel sample contains no visible water drops or particulates and is free of haze or cloudiness.

DHDS diesel

Before treatment

After treatment

Figure 2 Feed and product diesel samples of vacuum dryer at lab

Catalysis 2024