Effective Condensate & Flash Steam Recovery in the Chemical Industries
Narayan A Korde
Head - Energy Audit & Consultancy
Pennant Engg Pvt Ltd

Condensate and flash steam recovery in chemical industry is always a big challenge may be due to lack of knowledge about condensate commercial value, remote locations of chemical units inside the plant and potential contamination chances of condensate. Being one of the purest forms of water and rich heat source, captive utilization of condensate in the units or as makeup to cooling tower should be avoided. Recovery of condensate using steam operated condensate transfer pump instead of conventional electrical pump for pure condensate and using condensate contamination detection system for potential prone to impure condensate ensures effective utility cost reduction.

In India, typical condensate recovery in chemical and pharmaceutical industries ranges between 30 to 55 percent. Average direct steam consumption, this means that knowingly or unknowingly, around 35 to 70 per cent of the condensate, along with significant quantity of heat is being drained to increase the load of the effluent treatment plant (ETP).

Energy cost is the major concern in Indian industries as it directly affects the bottom line of the plant economy. Steam being one of the most widely used utility, the maximum utilization of the steam and effective recovery of the remaining heat in the form of condensate is a need of an hour to survive and grow in the market.

Also, generally, in India, location of chemical industries is in the remote, where water is always one of the scarcest utility to make it available. Even though the borewell or ground water is one of the option, its hardness and TDS is always a big concern as it not only increases the chemical and other treatment costs but also creates major damages due to scaling.

Hence, being important WR to its importance as a purest form of water as well as rich source of heat energy, it is inevitable to recover the condensate.

Affecting the Condensate Recovery
Following factors play a vital role that becomes hinderance in recovering the condensate.
  • Remotely located units in the plant
  • Less quantity of condensate making it practically non-feasible to recover
  • Scarcity of the water thereby imposing the use of condensate locally
  • Lack of knowledge about the value of condensate
Out of all the above and many more, "Lack of Knowledge" about the condensate ranks the first. Even at most of the industries, it has been observed that the condensate is stored in the tank outside the unit and pumped electrically to cater the make-up water demand of the nearby cooling towers. This not only wastes the pure condensate with its associated heat energy but also result in increasing the load on the cooling tower itself...!!!

Figure 1:

The recovery of the condensate can be classified into two simple categories:
1. Pure Condensate Recovery
2. Prone to be Impure Condensate Recovery
Figure 2:

1) Pure Condensate Recovery
This is feasible where steam is used for indirect heating the process fluid and virtually no chances of product or system generated contaminations observed. Typical applications include the condensate recovery from Fluid Bed Dryer (FBD), Hot Water Generation (HWG) systems, Hot water batteries, first effect of the Multiple Effect Evaporator (MEE) for ETP Unit, etc.

Few chemical industries have separate arrangement for steam coils and other process fluids like chilled water, cooling water, brine, hot water, etc, from which the pure condensate may be collected.

Conventional System
Conventionally, the condensate generated after indirect heating is collected in the tank located normally outside the unit and finally pumped to the feed water tank in the boiler house or any relevant desired location. The schematic of the same is shown in Figure 1.

As schematically represented, huge amount of heat energy is wasted due to improper handling of flash steam, ie, generated due to considerable highpressure condensate getting exposed to atmospheric pressure. Improper mixing of the hot condensate with the cold makeup water into the feed water tank also contributes to significant heat loss. Also, unnecessary make-up water intake caters to considerable amount of cooling of the condensate in the feed water tank and it becomes important to address the same in order to minimize captive consumption of steam in the feed water tank.

Major Areas of Concern in the Conventional System
  • No flash steam recovery, which contributes to around 40 to 50 per cent of the heat content in the flash steam
  • High operating cost due to running of electrical pump
  • High maintenance cost of the electrical pump being mechanical in operation as well as due to handling of condensate with high temperature
  • High capital cost due to requirement of tank with insulation, electrical pumps (at least 1 working and 1 standby) with proper weatherproof covering
Recommendation for the Pure Condensate
It is highly recommended to generate and utilize the flash steam by using the properly sized flash vessel and recover the condensate by means of steam or compressed air operated condensate transfer pump. A simple level transmitter based make-up water controlling system with negligible investment may pay very high returns in terms of avoiding the unnecessary intake of cold water intake. Proposed system of the effective flash steam and condensate recovery and ensuring its proper mixing in the boiler feed tank may be schematically represented is shown in Figure 2.

Significance of the Steam-operated Condensate Recovery System
  • Intrinsically safe for use in hazardous areas.
  • No electricity required - negligible operating costs.
  • Single spring design and no rotating parts ensures balance movement of float due to uniform expansion/contraction.
  • Only movable part - minimum chances of failure.
  • All stainless-steel internals give excellent corrosion resistance for long trouble-free service.
  • Negligible cost of operation.
  • No maintenance costs.

Figure 3:

Figure 4:

2) Recovery of the Condensate Prone to be Impure

The major concern of most of the industries lies in utilizing the condensate from the process equipment, which, due to its process chemicals or even the process operations, is very much susceptible to get contaminated. Chemical reactors, jacketed vessels, vapour collected from multiple effect evaporator (usually 2nd effect onwards), chemical processes heating to highly acidic products or intermediaries (eg, HF heating, Oxalate warm bath, etc).

Factors Resisting the Contaminated Condensate to Drain to ETP
  • Due to huge number of reactors, high quantum of condensate and its associated heat energy may get wasted.
  • Draining the condensate to ETP increases load on the ETP thereby increases effluent treatment cost.
  • Mixing of high temperature condensate in the ETP increases the efforts to cool down to desired temperature prior to treating it.
  • Stringent government norms limit the quantum of liquid discharge from the plant. This also increases the number of processes required to treat the effluent.
Typically, the prone to impure condensate is drained locally. The schematic of the same is shown in Figure 3.

Recommendation for the Potential Impure Condensate
Looking towards the commercial value of the condensate getting drained due to fear of probable contamination, it is recommended to install a highly reliable, efficient yet costeffective system that will help to collect and transfer the good quality of condensate and divert or drain the contaminated condensate which may go to drain or for the further treatment of purification.

Condensate Contamination Detection System (CCDS
It is a system, ie, based on the simple principle of change in the conductivity of the condensate when it is pure or contaminated. Normally, the contamination is either product contamination (like process fluid - HF, Lye, Oxalate, Chelates, etc) or the corrosion of the pipes like oxides of Iron (Fe2O3, FeO) or minerals, etc. Normally, condensate, being one of the purest forms of water, has negligible or very less conductivity. However, after contamination, the conductivity increases in multiples. When the conductivity increases beyond minimum acceptable limit (normally termed as a set point of the PID controller), the controller signals to divert or drain the impure condensate thereby eliminating the chances to get it into the boiler system.

Significant of the Condensate Contamination Detection System
  • Can differentiate and handle contamination even upto few micro Siemens (μS).
  • Recovered condensate followed by properly installed condensate and flash steam recovery system virtually recovers complete mass and heat content in the condensate.
  • Fully automatic system, no manual intervention needed.
  • If required, system cleaning or maintenance can be done online.
Proposed System with Condensate Contamination Detection System

Practically, by installing the condensate contamination detection system, is shown in Figure 4, condensate recovery may be increased from 15 to 40 per cent even. The typical payback ranges from couple of months to less than a year depending upon the condensate load, chances of contamination and the severity of the contamination.