Suggestions Required on Tank Design

Not enough information has been given for arriving at a decent answer.

Are you heating the water from 70° input to 90° output; or from some colder temperature to anywhere in the range of 70°-90°? Celsius or Fahrenheit?

What is the flow rate of the water to be heated: 150m³ per what unit of time?

What is the steam pressure and/or saturated temperature?

How much boiler capacity is available?

Sorry

We have got water at room temperature and will raise it to 70 to 90 deg C. 150m3/hr is a requirement, Steam is available in abundance at 15kpa,

Actually, our main heater needs some major repairs and they will take atleast a month. So this tank is going to be an intermin arrangement to make up for hot process water, it is not an essential requirement to produce exactly same capacity with same temp but closer to the original specs would be fantastic.

You may require about 20 tonnes of steam per hour to raise the temp of 150 m3/hr water by 70 deg C. It is better to use an open tank instead of closed one. A concrete or steel tank of required strength can be used. Let water and steam should enter from opposite directions. Steam pipe should not touch the tank walls to avoid vibrations due to surging of condensation. Let it enter from top and go down straight to tank bottom and trifurcate into three (or more) branches along the length of tank bottom. These branch pipes shall have several nozzles (or holes of 5 to 10 mm dia) opening upwards.

Water inlet to the tank shall be free from top with level control using float or control valve. Water outlet from bottom connecting to pump for process use.

I disagree with pritam.......

And I believe that you still have note offered enough information about your process needs.

What is the flow demand for the heated water ? Is there a steady demand or a variable demand ?

Since water is being heated and since steam is available, your best design option may be to use a "steam sparging heater" (beware of the noise)

See the tank sparger information at Spirax Sarco (www.spiraxsarco.com)

Alternately, consider the use of a quality direct injection steam heater, like the USA developed and made "Pick heater"

www.pickheaters.com .... or perhaps just buy a cheap Chinese or Indian substitute

Whatever you decide to do, make sure that you never come back to this forum and tell us......

That way we can never be sure that we helped you, or that you finally solved your problem

Flow demand is variable, sometime peaking to 300m3/hr however, as its just a temporary measure to make up the shortage, we are fine with 150. I will go through the linkc provided and will see the possibility of using either of them

Thanks Pritam and everyone,

Storage tank & heating with steam , coils, insulation blah blah is very costly and not viable as you said that your main heater will be repaired within a month. Please go an order a standby heater (which you should have done in the first place) maybe 100% identical or alfa lavel heat exchanger plates or Spirax/armstrong instant hot water generators.

Well, if we replace the existing setup with new one, it costs more than 800k but temporary setup also seems quite expensive. Still in negotiation with process guys to organize small setup to make up for the process water loss.

Frankly, you are just been set up as an escape-goat to put all the blames. Your Owner or the Consultant in the first place did not put 2 sets and opted a big x 1 set. This should have been 150 m3/hr x 2 instead 300 m3/hr x 1. All suggestions you are taking is simply wasting time for, not only these are not viable:direct steam injection via perforated pipes/ pick heaters/ steam injection etc., you will lose all your steam which will condense. Anyway, this alternate system will occupy space(remember the tank) and will take minimum 60 days to be fabricated and commissioned. After that it will never be used because your existing will be repaired & ready. Who will take the blame?

The thing is, if we lose Process Water for 1 month, we are unable to make slurry with required viscosity and it will cost millions. We have 2 process heater, each with capacity 300m3 but the requirement lies between 500 to 700m3/hr. If 1 heater is down, we will reduce throughput and ultimately lose production. So we are willing to spend some bucks to produce as much process water as we can during downtime and management has no objections at all. Secondly, after this major repair, we will turn to the other heater and will plan out its refurbish accordingly.

Ok under this condition the fastest is you take a Spirax 3-way mixing Valve (port B cold water. Port A Steam. Port AB = Hot water at 80-90C.

Here you do not need to make any storage tank or put in coils .A simple 3-way valve with an electric/pneumatic actuator with a temperature controller 0-100C. (this is exactly similar to pick Heaters). Install this valve's port AB on the outlet main of the present heat exchanger outlet main. give steam in Port A & Cold water in Port B.

You need to size the valve for the flow m3/hr . You might require sets of these 3-way valves to meet the total flow of 150 m3/hr as a battery. ask Spirax Engineering to do this.

Remember, the steam will condense and mix with the cold water and you cannot recover this. This will solve your immediate problem with just the cost of the 3-way Mixing valve. if in India contact Forbes marshall. if in Pakistan contact Aneeq Siddiqui, elsewhere contact Spirax Sarco.

Also the added cost of chemical treatment.