Influence of Salt Dosage and Hardness On Series Softener Performance
Authors: Bradley B.W. 
Published: December 2007

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.

This paper was prepared for the 42nd Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Houston, Tex., Oct. 1–4, 1967. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Laboratory and field experiments revealed that series sodium ion exchangers could produce softer water more consistently than conventional one-stage softeners. The amount of regeneration salt and calcium-magnesium contamination in the salt affect the quantity and quality [hardness] of the softened water. Regardless of regeneration variables, low hardness of the product water made regeneration with less salt possible and reduced costs by about 50 percent.

Introduction

During the summer of 1963 Shell Oil Co. added a second stage of water softeners to a commercial steam flood project. These additional softeners were added to produce softer water than possible with single-stage softening. Improved water quality was predicted from laboratory and field test data. The purpose of the tests described in this report was to determine the influence of brine dosage and hardness on the quality of the softened water.

EQUIPMENT

The softeners and piping arrangement used during the test period are shown in Fig. 1. The primary softeners produced into a common manifold. All polishing softeners received water from this manifold. Each primary and secondary softener train regenerated independently of the other trains. Abnormal performance of any primary softener influenced the feedwater to all polishing softeners and affected their product. Table 1 summarizes the characteristics of the series softening plant.

The size of the polisher was selected rather arbitrarily. It was based on the resin manufacturer's report that service flow rate could be increased from 2 to 10 gal/min/cu ft 17 to) 35 gal/min/sq ft for the polishers in this case] with a capacity loss of less than 5 percent. Although there was no intention of using the polisher to increase softener capacity, this data establisher permissible flow rates for the polisher.

RAW WATER

Table 2 presents a water analysis typical of the raw water supply to this plant during the test period.

TEST PROCEDURE

All tests were conducted on softener train 1. Regeneration of trains 2 and 3 were spot checked during the testing period. Any abnormal operation in any train negated the test performance evaluation of train 1.