Crop Processing PSAE

The purposeful movement of air at a low rate through a product to maintain or improve product quality. Air flow rates usually do not exceed 0.08 cubic meters per minute per cubic meter of product (0.1 cubic feet per minute per bushel of product) through a dry product and 0.80 cubic meters per minute per cubic meter of product (1cubic feet per minute per bushel of product) through a wet product.

aeration

The temperature of the surrounding air.

ambient temperature

In drying a harvested crop, the quantity of heat in air that can be utilized in evaporating water from the product.

available heat

A quantity of a harvested crop put into a bin or container on a repetitive basis specifically for treatment, such as drying.

batch

The process of mixing two or more different products together, such as grains and supplements, to obtain desired food ratios, or the process of mixing different quantities of the same product with different moisture contents to obtain a final mass with a uniform moisture content.

blending

by volume equals 1.25 cubic feet.

bushel

weight of grain defined by government grain standards as a standard unit for trading at a specific moisture (e.g. 56 pounds at 15.5 percent w.b.for number 2 corn).

dry bushel

is the weight of wet grain which when dried will give one dried bushel as specified in paragraph above (e.g. 63.5 lb of 25.5 percent w.b. corn).

wet bushel

Any component of a dryer, or dryer heat source, so designed to affect or limit any normal or abnormal condition of the drying operation.

control

That portion of the product mass in storage where the product temperature of the crop is falling during aeration.

cooling zone

Volumetric measure of quantity of flow.

Cubic meters per minute (CFM)

A form of conditioning as opposed to simple drying in which a chemical change occurs, such as in tobacco, sweet potatoes, etc., to prepare the crop for storage or use.

curing

Type of operation wherein application of maximum heat is periodic such as cycling between high fire and low fire, cycling between high fire and constant pilot; and cycling from high fire to “off”, then restarted to high fire by constant or intermittent ignition.

cycling burner

The rapid removal of moisture, usually to a very low level.

dehydration

When drying with air, a depth which would contain enough product that, if all the theoretical heat available for drying could be used, it would all dry to equilibrium in a period of time equal to the time required for the fully exposed product to dry half-way to equilibrium.

Depth factor (Df)

A unit which provides the conditions for removing moisture from a product.

dryer

Any dryer wherein the product to be dried is placed in the dryer, the complete drying or drying and cooling operation performed, and then removed for storage or further processing.

Batch dryer

A batch dryer equipped to circulate or mix the product during the drying and cooling period.

circulating dryer

A type of continuous flow dryer wherein the product being dried moves in the same direction as drying air. Sometimes referred to as parallel flow.

concurrent flow dryer

Any dryer wherein the product to be dried is in continuous movement through the dryer and air movement is continuous, in contrast to batch operation.

continuous flow dryer

A type of continuous-flow dryer wherein the product being dried moves in one direction and the drying air moves in the opposite direction.

counter flow dryer

A type of dryer wherein the flow of air is transverse to the direction of the flow of the product being dried.

cross flow dryer

Type of dryer in which the products of combustion come into direct contact with the product being dried.

direct-fired dryer

A dryer where the product is in suspension, or is moved through the dryer by the drying and/ or the cooling air.

fluidized or spouted bed dryer

Type of dryer in which the products of combustion do not come in contact with the products being dried.

indirect-fired dryer

A dryer in which the drying bin or compartment is also used to store the product after it is dried.

in-storage dryer

Any dryer manufactured as a package unit consisting of the drying and cooling chamber, necessary heat or radiation source, all AMD’s and duct work, along with the necessary controls and product handling equipment. These dryers may be either fixed or portable.

self-contained dryer

A type of dryer wherein the product being dried is conveyed through a tunnel-like chamber. It may be continuous or batch-type

tunnel dryer

The removal of moisture from a product, usually to some predetermined moisture content.

drying

The air being passed through the product which is being dried.

drying air

The temperature of the air entering the product being dried.

drying air temperature

The divisional layer between dried and undried products in drying systems.

drying front

The band or layer of product in which most of the drying is occurring at any instant.

drying zone

Act or process by which an electric conductor becomes electrified when near a charged body.

electrical induction

The moisture content of a product when it is in equilibrium with the surrounding atmosphere

equilibrium moisture content

The relative humidity of air surrounding the product in equilibrium with given moisture content. The air and product are at the same temperature.

equilibrium relative humidity

A control designed so that a malfunction of any of its components will stop the operation of the device or equipment controlled by it.

fail-safe control

mounted on the grain dryer structure and connected to the gas burner, includes all piping components of fuel flow control and safety shut-off valves.

fuel train

A device used to transfer heat from one fluid stream to another without intermixing.

hear exchanger

Use of forced ventilation with the addition of heat for removing moisture.

heating-air drying

A type of fitting designed to prevent galvanic current flow when used between two dissimilar metals.

insulating fitting

A measure of quantity of heat. One _____ will raise the temperature of one gram of water one degree Celsius.

joule

A measure of quantity of heat. One _____ will raise the temperature of one pound of water one degree Fahrenheit.

BTU

The pressure of the fuel in the supply line to the dryer

line pressure

A mixture of gaseous petroleum products normally stored and transported as a liquid under pressure. The principal constituents are propane and butane.

LPG

For products, expressed as percentage, by weight, of water in the product divided by dry matter.

MCdb

For agricultural producers, usually expressed as percentage, by weight, of water in the product, wet basis.

MCwb

A gaseous hydrocarbon, odorless and flammable, found in its natural state in particular geologic formation as a product of decomposition of organic matter. The composition is chiefly of the methane series with varying amounts of other components such as carbon dioxide, hydrogen, and helium often being present.

natural gas

The opening through which gas is admitted to the burner.

orifice

The pilot remains lit during the time power is supplied to the burner.

pilot-continuous

The pilot is lit during the time combustion is being established. When combustion is established the pilot is de-energized.

pilot-interruptible

The pilot is manually lit and remains lit until manually shut off.

pilot-standing

An air chamber maintained under pressure (positive or negative) usually connected to one or more distributing ducts in a drying or aeration system. The term is also used to designate the air chamber under the perforated floor in a grain bin and the pressure chamber between grain columns in some types of batch or continuous dryers.

plenum

A mechanical device which reduces the fluid (liquid or gas) pressure to a relatively constant delivery pressure while the inlet pressure may vary and while the volume of gas may also vary.

pressure regulator

refers to clearing or purging the plenum chamber or duct of any volatile gases prior to ignition of the burner. It is usually by a device which ensures that the fan must operate for a certain preiod of before ignition will be permitted.

pre-ventilation

The process by which energy is emitted from molecules and atoms owing to the internal changes. Also the combined process of emission, transmission, and absorption of radiant energy.

radiation

As applied to crop dryers, the term refers to the return of the portion of the exhaust air to the air intake of the dryer, or to the return of underdried grain to the dryer or container from which it was removed.

recirculation

A measure of the moisture content of air expressed as a percentage.

moisture content

A measure of air pressure usually expressed in pascals [inches of water column (WC)].

static pressure

Condition when the operation or process reaches equilibrium.

steady state

Continuous monitoring to react automatically to flame failure so as to shut off gas flow to the unit.

supervision

Any heat added to that already present in the atmosphere to obtain a limited temperature rise, usually less than 11°C (20°F), to accomplish drying within the maximum permissible drying time to prevent spoilage.

supplemental heat

As applied to crop drying, the term refers to the difference between ambient temperature and the temperature and the temperature of the drying air resulting from the addition of heat by the dryer burner.

temperature rise

Equilization of moisture or temperature throughout the product. Bringing a product to a desired moisture content or temperature for processing.

tempering

The elapsed time from the start of the drying process to the instant the drying front arrives at any point or place in the product.

time of drying

Time required to dry fully exposed products halfway to equilibrium.

time of one-half response

The process of moving a product through the air within a bin or storage structure, or from one bin or storage structure to another.

turning

A check valve which permits flow of fluid in either direction but which limits excessive flow in one direction. If the designated flow is exceeded, the valve automatically closes.

excess-flow valve

A valve designated as a safety device to open, and remain open, to discharge a fluid whenever the fluid pressure reaches the start-to-discharge setting of the valve. When the fluid pressure drops below this setting, the relief valve automatically closes.

pressure-relief valve

A manually operated valve specially designed to accomplish rapid shut-off to fuel flow to dryer.

quick-acting valve

A valve which is opened or closed by a solenoid (electromagnet). In the normally closed type, for example, the valve is opened by the solenoid but closed by a return spring and held closed by the fluid pressure upstream from the valve.

solenoid valve

Commonly taken to mean saturated vapor pressure which is the vapor pressure of a vapor in contact with its liquid form. An example is the pressure in an LP-gas storage tank. The term is also used for the pressure of the vaporized fuel being fed to the burner orifice.

vapor pressure

is a heat exchanger wherein heat is supplied to change the liquid fuel to vapor, ready for combustion.

vaporizer

The rate of air flow determined by dividing the quantity of air flow in cfm by the cross-sectional area.

apparent velocity

The rate of air travel through product void space. It is determined by dividing the apparent velocity by the product void space expressed as a decimal. It is always greater than apparent velocity

average velocity

Air movement through space.

ventilation

The locus of all points of equal traverse time in the product being conditioned.

ventilation front

The space between particles in a bulk of stored crop, usually expressed as percent of total volume.

void space